Document Entity Information Statement	12 Months Ended
Document Entity Information Statement	Sep. 30, 2018 shares
Document Information [Abstract]
Entity Registrant Name	Autolus Therapeutics plc
Entity Central Index Key	0001730463
Document Type	20-F
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	true
Entity Small Business	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	40,146,182

Consolidated Balance Sheets - USD ($)	Sep. 30, 2018	Sep. 30, 2017
Current assets:
Cash	$ 247,089,000	$ 137,070,000
Prepaid expenses and other current assets	12,189,000	5,412,000
Total current assets	259,278,000	142,482,000
Non-current assets:
Property and equipment, net	13,528,000	6,180,000
Intangible assets, net	399,000	0
Total assets	273,205,000	148,662,000
Current liabilities:
Accounts payable	3,036,000	1,946,000
Accrued expenses and other liabilities	14,103,000	3,087,000
Total current liabilities	17,139,000	5,033,000
Non-current liabilities:
Long-term lease incentive obligation	221,000	265,000
Other long-term payables	380,000	763,000
Total liabilities	17,740,000	6,061,000
Shareholders' equity:
Additional paid-in capital	357,918,000	194,351,000
Accumulated other comprehensive loss	(9,920,000)	(3,849,000)
Accumulated deficit	(92,653,000)	(47,902,000)
Total shareholders' equity	255,465,000	142,601,000
Total liabilities and shareholders' equity	273,205,000	148,662,000
Ordinary shares
Shareholders' equity:
Shares value	2,000	1,000
Deferred Shares
Shareholders' equity:
Shares value	0	0
Deferred B shares
Shareholders' equity:
Shares value	118,000	0
Deferred C shares
Shareholders' equity:
Shares value	$ 0	$ 0

Consolidated Balance Sheets (Parentheticals)	Sep. 30, 2018 £ / shares shares	Sep. 30, 2018 $ / shares shares	Sep. 30, 2017 £ / shares shares	Sep. 30, 2017 $ / shares shares
Ordinary shares
Shareholders' equity:
Common stock, par value (usd/gbp per share) \| (per share)		$ 0.000042		$ 0.000042
Common stock, shares authorized (shares)	200,000,000	200,000,000	37,426,509	37,426,509
Common stock, shares, issued (shares)	40,146,182	40,146,182	29,962,742	29,962,742
Common stock, shares outstanding (shares)	40,146,182	40,146,182	29,962,742	29,962,742
Deferred Shares
Shareholders' equity:
Common stock, par value (usd/gbp per share) \| £ / shares	£ 0.00001		£ 0.00001
Common stock, shares authorized (shares)	34,425	34,425	0	0
Common stock, shares, issued (shares)	34,425	34,425	0	0
Common stock, shares outstanding (shares)	34,425	34,425	0	0
Deferred B shares
Shareholders' equity:
Common stock, par value (usd/gbp per share) \| £ / shares	£ 0.00099		£ 0.00099
Common stock, shares authorized (shares)	88,893,548	88,893,548	0	0
Common stock, shares, issued (shares)	88,893,548	88,893,548	0	0
Common stock, shares outstanding (shares)	88,893,548	88,893,548	0	0
Deferred C shares
Shareholders' equity:
Common stock, par value (usd/gbp per share) \| £ / shares	£ 0.000001		£ 0.000001
Common stock, shares authorized (shares)	1	1	0	0
Common stock, shares, issued (shares)	1	1	0	0
Common stock, shares outstanding (shares)	1	1	0	0

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Grant income	$ 1,407	$ 1,693	$ 1,212
Operating expenses:
Research and development	(36,150)	(16,012)	(10,436)
General and administrative	(22,790)	(9,099)	(5,152)
Total operating expenses, net	(57,533)	(23,418)	(14,376)
Other income (expense):
Interest income	1,532	84	75
Other income (expense)	3,970	(46)	(26)
Total other income, net	5,502	38	49
Net loss before income tax	(52,031)	(23,380)	(14,327)
Income tax benefit	7,280	3,653	1,777
Net loss attributable to ordinary shareholders	(44,751)	(19,727)	(12,550)
Other comprehensive (loss) income:
Foreign currency exchange translation adjustment	(6,071)	802	(2,942)
Total comprehensive loss	$ (50,822)	$ (18,925)	$ (15,492)
Basic and diluted net loss per ordinary share (usd per share)	$ (1.42)	$ (1.43)	$ (1.26)
Weighted-average basic and diluted ordinary shares (shares)	31,557,034	13,783,222	9,933,399

Consolidated Statements of Shareholders’ Equity Statement - USD ($) $ in Thousands	Total	Ordinary shares	Deferred Shares	Deferred B shares	Deferred C Shares	Common shares Ordinary shares	Common shares Deferred Shares	Common shares Deferred B shares	Common shares Deferred C Shares	Additional Paid in Capital	Accumulated other comprehensive loss	Accumulated deficit
Beginning balance at Sep. 30, 2015	$ 10,501					$ 0	$ 0	$ 0	$ 0	$ 27,835	$ (1,709)	$ (15,625)
Beginning balance (shares) at Sep. 30, 2015						6,713,663	0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance, net of issuance cost	33,421									33,421
Issuance, net of issuance cost (shares)						7,207,881
Share-based compensation expense	2,257									2,257
Unrealized loss on foreign currency translation	(2,942)										(2,942)
Net loss	(12,550)											(12,550)
Ending, balance at Sep. 30, 2016	$ 30,687					$ 0	$ 0	$ 0	$ 0	63,513	(4,651)	(28,175)
Ending balance (shares) at Sep. 30, 2016	13,921,543					13,921,544	0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance, net of issuance cost	$ 127,686					$ 1				127,685
Issuance, net of issuance cost (shares)						16,041,198
Share-based compensation expense	3,153									3,153
Unrealized loss on foreign currency translation	802										802
Net loss	(19,727)											(19,727)
Ending, balance at Sep. 30, 2017	$ 142,601					$ 1	$ 0	$ 0	$ 0	194,351	(3,849)	(47,902)
Ending balance (shares) at Sep. 30, 2017	29,962,741					29,962,742	0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance, net of issuance cost	$ 156,803					$ 1		$ 118	$ 0	156,802
Issuance, net of issuance cost (shares)						10,183,440	34,425	88,893,548	1
Share-based compensation expense	6,765									6,765
Unrealized loss on foreign currency translation	(6,071)										(6,071)
Net loss	(44,751)											(44,751)
Ending, balance at Sep. 30, 2018	$ 255,465					$ 2	$ 0	$ 118	$ 0	$ 357,918	$ (9,920)	$ (92,653)
Ending balance (shares) at Sep. 30, 2018	129,074,156	40,146,182	34,425	88,893,548	1	40,146,182	34,425	88,893,548	1

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Consolidated Statement of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net loss	$ (44,751)	$ (19,727)	$ (12,550)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,709	1,009	478
Loss on disposal of fixed assets	8	0	0
Non-cash share-based compensation	6,765	3,153	2,257
Non-cash consideration for licenses	0	0	1,199
Changes in operating assets and liabilities
Prepaid expenses and other current assets	(7,132)	(2,317)	(2,048)
Accounts payable	838	434	507
Accrued expenses and other liabilities	11,026	1,088	308
Net cash used in operating activities	(31,537)	(16,360)	(9,849)
Cash flows from investing activities:
Purchases of property and equipment	(9,119)	(2,876)	(1,855)
Purchase of intangible assets	(412)	0	0
Net cash used in investing activities	(9,531)	(2,876)	(1,855)
Cash flows from financing activities:
Proceeds of issuance of ordinary shares, net of issuance costs	156,920	127,686	32,222
Net cash provided by financing activities	156,920	127,686	32,222
Effect of exchange rate changes on cash	(5,833)	561	(2,662)
Net increase in cash	110,019	109,011	17,856
Cash, beginning of year	137,070	28,059	10,203
Cash, end of year	247,089	137,070	28,059
Supplemental Cash Flow Information
Property and equipment purchases included in accounts payable	$ 328	$ 0	$ 0

Nature of the Business

12 Months Ended

Sep. 30, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of the Business

Autolus Therapeutics plc (the “Company”) is a biopharmaceutical company developing next-generation programmed T cell therapies for the treatment of cancer. Using its broad suite of proprietary and modular T cell programming technologies, the Company is engineering precisely targeted, controlled and highly active T cell therapies that are designed to better recognize cancer cells, break down their defense mechanisms and attack and kill these cells. The Company believes its programmed T cell therapies have the potential to be best-in-class and offer cancer patients substantial benefits over the existing standard of care, including the potential for cure in some patients.

The Company is a public limited company incorporated in England and Wales. On June 15, 2018, the Company completed the first step of a corporate reorganization, pursuant to which the shareholders of Autolus Limited, a private company originally incorporated under the laws of England and Wales in July 2014 as NewIncCo 1311 Limited which subsequently changed its name to Autolus Limited in August 2014, exchanged each of the different classes of shares held by them in Autolus Limited for the same number and class of newly issued ordinary shares of Autolus Therapeutics Limited. As a result, Autolus Limited became a wholly owned subsidiary of Autolus Therapeutics Limited, a holding company incorporated in February 2018 with nominal assets and liabilities, which has not conducted any operations prior to the share exchange and other actions incidental to the exchange and its incorporation. Following Autolus Limited becoming a wholly owned subsidiary of Autolus Therapeutics Limited, Autolus Therapeutics Limited transferred the entire issued share capital of Autolus Limited to Autolus Holdings (UK) Limited. Shortly thereafter, Autolus Therapeutics Limited, and Autolus Holdings (UK) Limited reduced their respective issued share capital pursuant to Part 17 of the Companies Act.

On June 18, 2018, as the second step of the corporate reorganization, Autolus Therapeutics Limited re-registered as a public limited company and its name was changed from Autolus Therapeutics Limited to Autolus Therapeutics plc. Following the re-registration of Autolus Therapeutics Limited as a public limited company, Autolus Limited reduced its issued share capital pursuant to Part 17 of the Companies Act by way of the cancellation of all of its issued series A preferred shares, C ordinary shares, deferred shares and all but 100 B ordinary shares.

The corporate reorganization took place in several steps, all of which have been completed. We refer to the following steps, which are discussed in more detail below, as our “corporate reorganization”:

•

Exchange of Autolus Limited Shares for Autolus Therapeutics Limited Shares: All shareholders of Autolus Limited have exchanged each of the shares held by them for the same number and class of newly issued shares of Autolus Therapeutics Limited and, as a result, Autolus Limited became a wholly owned subsidiary of Autolus Therapeutics Limited. Following the share exchange, holders of options over shares in Autolus Limited agreed to exchange their existing options for new options granted by Autolus Therapeutics Limited over shares in Autolus Therapeutics Limited (now called Autolus Therapeutics plc).

•

Transfer of Autolus Limited Shares to Autolus Holdings (UK) Limited: Immediately after the share exchange, Autolus Therapeutics Limited transferred the entire issued share capital of Autolus Limited to Autolus Holdings (UK) Limited and, as a result, Autolus Limited became a wholly owned subsidiary of Autolus Holdings (UK) Limited, which itself was a wholly owned subsidiary of Autolus Therapeutics Limited.


•	Reduction of Capital of Autolus Therapeutics Limited, Autolus Holdings (UK) Limited and Autolus Limited: Autolus Therapeutics Limited, Autolus Holdings (UK) Limited and Autolus Limited reduced their issued share capital pursuant to Part 17 of the Companies Act.


•	Re-registration of Autolus Therapeutics Limited as a Public Limited Company and Change of Name to Autolus Therapeutics plc.


•	Reorganization of Separate Classes of Shares of Autolus Therapeutics plc into a Single Class of Ordinary Shares: The different classes of issued share capital of Autolus Therapeutics plc were reorganized into a single class of ordinary shares on a 3.185-for-1 basis and various classes of deferred shares were created.


•	Autolus Therapeutics plc redenominated its existing ordinary shares from British pounds to U.S. dollars.

On June 22, 2018, the different classes of the Company’s issued share capital were converted into a single class of ordinary shares and the Company completed its initial public offering ("IPO") of American Depositary Shares (“ADSs”). In the IPO, the Company sold an aggregate of 10,147,059 ADSs representing the same number of ordinary shares, including 1,323,529 ADSs pursuant to the underwriters’ option to purchase additional ADSs, at a public offering price of $17.00 per ADS. Net proceeds were approximately $156.5 million, after deducting underwriting discounts and commissions and offering expenses paid by the Company. Following the share capital reorganization of Autolus Therapeutics plc described above, each ordinary share with a nominal value of £0.000032 was redenominated as an ordinary share with a nominal value of $0.000042. The Company’s corporate reorganization is described further below.

Autolus Therapeutics plc is a continuation of Autolus Limited and its subsidiaries, and the corporate reorganization has been accounted for as a combination of entities under common control. The corporate reorganization has been given retrospective effect in these financial statements and such financial statements represent the financial statements of Autolus Therapeutics plc. In connection with the corporate reorganization, outstanding restricted share awards and option grants of Autolus Limited were exchanged for share awards and option grants of Autolus Therapeutics plc with identical restrictions.

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Product candidates currently under development will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize revenue from its product sales.

The Company has funded its operations primarily with proceeds from the sale of its equity securities. The Company has incurred recurring losses since its inception, including net losses of $44.8 million, $19.7 million and $12.6 million for the years ended September 30, 2018, 2017 and 2016, respectively. In addition, as of September 30, 2018 and 2017, the Company had an accumulated deficit of $92.7 million and $47.9 million, respectively. The Company expects to continue to generate operating losses for the foreseeable future. The future viability of the Company beyond that point is dependent on its ability to raise additional capital to finance its operations. The Company’s inability to raise additional capital as and when needed could have a negative impact on its financial condition and ability to pursue its business strategies. There can be no assurances, however, that the current operating plan will be achieved or that additional funding will be available on terms acceptable to the Company, or at all. The Company believes the cash on hand at September 30, 2018 of $247.1 million will be sufficient to fund the Company’s operations for at least 12 months from the issuance date of these financial statements.

Summary of Significant Accounting Policies

12 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Presentation

The accompanying consolidated financial statements include those of the Company, Autolus Limited, and its U.S. subsidiary, Autolus Inc., and have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). All intercompany accounts and transactions have been eliminated upon consolidation.

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of income and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the accrual for research and development expenses, the fair value of ordinary shares, the valuation of tranche obligations, share-based compensation and income taxes. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ materially from those estimates.

Cash and Cash Equivalents

The Company considers all highly liquid investments that have maturities of three months or less when acquired to be cash equivalents.

Fair Value Measurements

The carrying amounts reported in the balance sheets for cash, prepaid expenses and other assets, accounts payable and accrued expenses and other liabilities approximate their fair value because of the short-term nature of these instruments.

Concentration of Credit Risk

Financial instruments that subject the Company to credit risk consist primarily of cash and cash equivalents. The Company places cash and cash equivalents in established financial institutions. The Company has no significant off-balance-sheet risk or concentration of credit risk, such as foreign exchange contracts, options contracts, or other foreign hedging arrangements.

Property and Equipment

Property and equipment are recorded at cost and depreciated or amortized using the straight-line method over the estimated useful lives of the respective assets. As of September 30, 2018 and 2017, the Company’s property and equipment consisted of office equipment, lab equipment, furniture and fixtures, and leasehold improvements. The office equipment has an estimated useful life of three years and the lab equipment and furniture and fixtures have an estimated useful life of five years. Leasehold improvements are depreciated over the shorter of the lease term or the estimated useful life of the asset. Assets under construction consist of costs incurred with leasehold improvements and, once placed into service, will be depreciated over the shorter of the lease term or the estimated useful life of the asset. Upon retirement or sale, the cost of assets disposed of, and the related accumulated depreciation, are removed from the accounts and any resulting gain or loss is included in the statement of operations and other comprehensive loss. Repairs and maintenance expenditures, which are not considered improvements and do not extend the useful life of property and equipment, are expensed as incurred.

The Company evaluates an asset for potential impairment when events or changes in circumstances indicate the carrying value of the asset may not be recoverable. Recoverability is measured by comparing the book value of the asset to the expected future net undiscounted cash flows that the asset is expected to generate. If such asset is considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the asset exceeds the fair value. The Company has not recognized any impairment losses from its inception through September 30, 2017. The Company recognized asset disposal of less than $10,000 for the year ended September 30, 2018.

Intangible Assets Subject to Amortization

The Company’s intangible assets with finite lives are amortized over their useful lives and reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. If any indicators were present, the Company would test for recoverability by comparing the carrying amount of the asset to the net undiscounted cash flows expected to be generated from the asset. If those net undiscounted cash flows do not exceed the carrying amount (i.e., the asset is not recoverable), the Company would perform the next step, which is to determine the fair value of the asset and record an impairment loss, if any. The Company evaluates the useful lives for these intangible assets each reporting period to determine whether events and circumstances warrant a revision in their remaining useful lives. The Company’s intangible assets are not available for use and therefore no amortization has been charged to date.

Segment Information

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker in deciding how to allocate resources and assess performance. The Company and the Company’s chief operating decision maker, the Company’s Chief Executive Officer, view the Company’s operations and manages its business as a single operating segment, which is the business of developing and commercializing gene therapies; however, the Company operates in two geographic regions: the United Kingdom and the United States. Substantially all of the Company’s assets are held in the United Kingdom.

Deferred Rent and Lease Incentives

Rent expense and lease incentives from operating leases are recognized on a straight-line basis over the lease term. The Company has operating leases that include rent escalation payment terms and a rent free period. Deferred rent represents the difference between actual operating lease payments and straight-line rent expense over the term of the lease.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities, including salaries, share-based compensation and benefits, depreciation expense, third-party license fees, external costs of outside vendors engaged to conduct clinical development activities, clinical trials, costs to manufacture clinical trial materials and certain tax credits associated with research and development activities. The Company recorded the U.K.'s research and development expenditure credit, RDEC, of $0.2 million and $0.2 million for the years ended September 30, 2018 and 2017, respectively, as reductions of research and development expenses within the Company’s statement of operations and comprehensive loss.

Accrued Research and Development Expenses

As part of the process of preparing consolidated financial statements, the Company is required to estimate accruals for research and development expenses. This process involves reviewing and identifying services which have been performed by third parties on the Company’s behalf and determining the value of these services. In addition, the Company makes estimates of costs incurred to date but not yet invoiced, in relation to external CROs and clinical site costs. The Company analyzes the progress of clinical trials, including levels of patient enrollment; invoices received and contracted costs, when evaluating the adequacy of the accrued liabilities for research and development. The Company makes judgments and estimates in determining the accrued balance in any accounting period.

Share-Based Compensation

The Company recognizes compensation expense for equity awards based on the grant date fair value of the award. The Company recognizes share-based compensation expense for awards granted to employees that have a graded vesting schedule based on a service condition only on a straight-line basis over the requisite service period for each separately vesting portion of the award as if the award was, in substance, multiple awards (the “graded-vesting attribution method”), based on the estimated grant date fair value for each separately vesting tranche. For equity awards with a graded vesting schedule and a combination of service and performance conditions, the Company recognizes share-based compensation expense using a graded-vesting attribution method over the requisite service period when the achievement of a performance-based milestone is probable, based on the relative satisfaction of the performance condition as of the reporting date. For share-based awards granted to consultants and non-employees, compensation expense is recognized using the graded-vesting attribution method over the period during which services are rendered by such consultants and non-employees until completed. At the end of each financial reporting period prior to completion of the service, the fair value of these awards is remeasured using the then-current fair value of the Company’s ordinary shares. The Company accounts for forfeitures as they occur. Forfeitures to date have been infrequent and immaterial.

The fair value of each share option grant is estimated on the date of grant using the Black-Scholes option pricing model. See Note 7 for the Company’s assumptions used in connection with option grants made during the periods covered by these financial statements. Assumptions used in the option pricing model include the following:

Expected volatility. The Company lacks company-specific historical and implied volatility information for its ADSs. Therefore, the Company estimates the expected share volatility based on the historical volatility of publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded share price.

Expected term. The expected term of the Company’s share options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options.

Risk-free interest rate. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods that are approximately equal to the expected term of the award.

Expected dividend. Expected dividend yield of zero is based on the fact that the Company has never paid cash dividends on ordinary shares and does not expect to pay any cash dividends in the foreseeable future.

Fair value of ordinary shares. Options granted after the Company’s IPO are issued at the fair market value of the Company’s ADS at the date the grant is approved by the Board.

Prior to the IPO, the Company calculated the fair value of its ordinary shares in accordance with the guidelines in the American Institute of Certified Public Accountants’ Accounting and Valuation Guide, Valuation of Privately-Held-Company Equity Securities Issued as Compensation. The Company’s valuations of ordinary shares were prepared using a market approach, based on precedent transactions in the shares, to estimate the Company’s total equity value using the option-pricing method (“OPM”), which used a combination of market approaches and an income approach to estimate the Company’s enterprise value.

The OPM derives an equity value such that the value indicated is consistent with the investment price, and it provides an allocation of this equity value to each class of the Company’s securities. The OPM treats the various classes of shares as call options on the total equity value of a company, with exercise prices based on the value thresholds at which the allocation among the various holders of a company’s securities changes. Under this method, each class of shares has value only if the funds available for distribution to shareholders exceed the value of the share liquidation preferences of the class or classes of shares with senior preferences at the time of the liquidity event. Key inputs and assumptions used in the OPM calculation include the following:

Expected volatility. The Company applied re-levered equity volatility based on the historical unlevered and re-levered equity volatility of publicly traded peer companies.

Expected term. The expected term of the option or the estimated time until a liquidation event.

Risk-free interest rate. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve for the period commensurate with the expected of the exit event.

When considering the fair value of options granted in the period prior to the IPO, management considered probability-weighted scenarios based on the relative likelihoods of completing the IPO and remaining a privately-held company. In the IPO scenarios, the fair value was calculated by dividing the total estimated equity value by the number of fully diluted ordinary shares outstanding, and then discounting the implied per-share value at a rate intended to approximate the Company's cost of equity between share option grant date and the expected IPO date. The stay-private scenario utilized an OPM "Backsolve" calculation to estimate our equity value implied by the purchase price of the series A preference shares in September 2017. In March and May 2018, we issued share option grants to employees that applied a 50% and 80% probability weighting of an IPO, respectively, to the fair value of the underlying ordinary share utilized in the Black-Scholes option pricing model.

Foreign Currency Translation

The Company maintains its financial statements in its functional currency, which is the pounds sterling. Monetary assets and liabilities denominated in currencies other than the functional currency are translated into the functional currency at rates of exchange prevailing at the balance sheet dates. Non-monetary assets and liabilities denominated in foreign currencies are translated into the functional currency at the exchange rates prevailing at the date of the transaction. Exchange gains or losses arising from foreign currency transactions are included in the determination of net income (loss) for the respective periods. The Company recorded foreign exchange gain of $4.0 million and and foreign exchange loss of $25,000 for the years ended September 30, 2018 and 2017, respectively, which are included in other income in the statements of operations and comprehensive loss.

For financial reporting purposes, the financial statements of the Company have been translated into U.S. dollars. Assets and liabilities have been translated at the exchange rates at the balance sheet dates, while revenue and expenses are translated at the average exchange rates over the reporting period and shareholders’ equity amounts are translated based on historical exchange rates as of the date of each transaction. Translation adjustments are not included in determining net income (loss) but are included in foreign exchange adjustment to other comprehensive loss, a component of shareholders’ equity.

Patent Costs

The Company expenses patent prosecution and related legal costs as they are incurred and classifies such costs as general and administrative expenses in the accompanying statements of operations and comprehensive loss. The Company recorded patent expenses of $1.0 million and $0.5 million for the years ended September 30, 2018 and 2017, respectively.

Grant Income

The Company has received research grants under which it is reimbursed for specific research and development activities. Payments received are recognized as income in the statements of operations and comprehensive loss over the period in which the Company recognizes the related costs. At the time the Company recognizes grant income, it has complied with the conditions attached to it and the receipt of the reimbursement is reasonably assured. The Company has received grants from the U.K. government, which are repayable under certain circumstances, including breach or noncompliance. For grants with refund provisions, the Company reviews the grant to determine the likelihood of repayment. If the likelihood of repayment of the grant is determined to be remote, then the grant is recognized as grant income. The Company has determined that the likelihood of any repayment events included in its current grants is remote.

Income Taxes

The Company accounts for income taxes under the asset and liability method which includes the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s financial statements. Under this approach, deferred taxes are recorded for the future tax consequences expected to occur when the reported amounts of assets and liabilities are recovered or paid. The provision for income taxes represents income taxes paid or payable for the current year plus deferred taxes. Deferred taxes result from differences between the financial statements and tax bases of the Company’s assets and liabilities, and are adjusted for changes in tax rates and tax law when changes are enacted. The effects of future changes in income tax laws or rates are not anticipated.

The Company is subject to income taxes in the United Kingdom and the United States. The calculation of the Company’s tax provision involves the application of United Kingdom tax law and requires judgement and estimates.

The Company evaluates the realizability of its deferred tax assets at each reporting date, and establishes a valuation allowance when it is more likely than not that all or a portion of its deferred tax assets will not be realized.

The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income of the same character and in the same jurisdiction. The Company considers all available positive and negative evidence in making this assessment, including, but not limited to, the scheduled reversal of deferred tax liabilities, projected future taxable income, and tax planning strategies. In circumstances where there is sufficient negative evidence indicating that the Company’s deferred tax assets are not more likely than not realizable, the Company establishes a valuation allowance.

The Company uses a two-step approach for recognizing and measuring uncertain tax positions. The first step is to evaluate tax positions taken or expected to be taken in a tax return by assessing whether they are more likely than not sustainable, based solely on their technical merits, upon examination, and including resolution of any related appeals or litigation process. The second step is to measure the associated tax benefit or each position as the largest amount that the Company believes is more likely than not realizable. Differences between the amount of tax benefits taken or expected to be taken in the Company’s income tax returns and the amount of tax benefits recognized in the its financial statements represent the Company’s unrecognized income tax benefits, which it either records as a liability or reduction of deferred tax assets.

Income Tax Credit

The Company benefits from the U.K. research and development tax credit regime under both the small and medium sized enterprise, or SME, scheme and by claiming an RDEC in respect of grant funded projects. Under the SME regime, a portion of the Company’s losses can be surrendered for a cash rebate of up to 33.35% of eligible expenditures. Such credits are accounted for within the tax provision in the year in which the expenditures were incurred.

Comprehensive Loss

The Company follows the provisions of the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 220, Comprehensive Income, which establishes standards for the reporting and display of comprehensive income and its components. Comprehensive loss is defined to include all changes in equity during a period except those resulting from investments by owners and distributions to owners. The Company recorded a loss of $6.1 million, a gain of $0.8 million, and a loss of $2.9 million related to foreign currency translation during the years ended September 30, 2018, 2017 and 2016, respectively.

Net Loss per Share

Basic and diluted net loss per ordinary share is determined by dividing net loss by the weighted average number of ordinary shares outstanding during the period. For all periods presented, the preferred shares and outstanding but unvested restricted shares and share options have been excluded from the calculation, because their effects would be anti-dilutive. Therefore, the weighted average shares outstanding used to calculate both basic and diluted loss per share are the same for all periods presented.

The following potentially dilutive securities have been excluded from the calculation of diluted net loss per share due to their anti-dilutive effect:



	Year Ended September 30,
	2018	2017	2016
Unvested restricted incentive shares	815,632	1,358,317	1,266,619
Incentive share options	2,065,481	570,309	—
Total	2,881,113	1,928,626	1,266,619

Ordinary Share Conversion

On the date of the IPO, the Company converted its outstanding preferred and ordinary shares as discussed in Note 6. All share and per share information has been retroactively adjusted to reflect the share conversion.

Emerging Growth Company Status

The Company is an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act (“JOBS Act”) and may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies. The Company may take advantage of these exemptions until the Company is no longer an emerging growth company. Section 107 of the JOBS Act provides that an emerging growth company can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. The Company has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.

These exemptions provided by the JOBS Act will apply up until the last day of the fiscal year following the fifth anniversary of the IPO or such earlier time that the Company is no longer meets the requirements of being an emerging growth company. The Company would cease to be an emerging growth company if it has more than $1.07 billion in annual revenue, has more than $700 million in market value of its securities held by non-affiliates (and it has been a public company for at least 12 months, and has filed one annual report on Form 20-F), or it issues more than $1 billion of non-convertible debt securities over a three-year period.

JOBS Act

On April 5, 2012, the Jumpstart Our Business Startups Act, or the JOBS Act, was enacted. The JOBS Act provides that, among other things, an emerging growth company can take advantage of an extended transition period for complying with new or revised accounting standards. As an emerging growth company, the Company has irrevocably elected not to take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards and, as a result, the Company will comply with new or revised accounting standards on the relevant dates on which adoption of such standards is required for non-emerging growth public companies.

In addition, the Company intends to rely on the other exemptions and reduced reporting requirements provided by the JOBS Act. Subject to certain conditions set forth in the JOBS Act, the Company is entitled to rely on certain exemptions as an “emerging growth company.” As an emerging growth company, the Company is not required to, among other things, (i) provide an auditor’s attestation report on the Company’s system of internal controls over financial reporting pursuant to Section 404(b), (ii) provide all of the compensation disclosure that may be required of non-emerging growth public companies under the Dodd-Frank Wall Street Reform and Consumer Protection Act, (iii) comply with any requirement that may be adopted by the Public Company Accounting Oversight Board regarding mandatory audit firm rotation or a supplement to the auditor’s report providing additional information about the audit and the financial statements (auditor discussion and analysis), and (iv) disclose certain executive compensation-related items such as the correlation between executive compensation and performance and comparisons of the chief executive officer’s compensation to median employee compensation. These exemptions will apply for a period of five years following the completion of the IPO or until the Company no longer meets the requirements of being an emerging growth company, whichever is earlier.

Recently issued accounting pronouncements not yet adopted

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”), which requires a lessee to recognize certain leases on the balance sheet but recognize expenses on the income statement in a manner similar to current accounting standards practice. The update states that a lessee will recognize a lease liability for the obligation to make lease payments and a right-to-use asset for the right to use the underlying assets for the lease term. Leases will continue to be classified as either financing or operating, with classification affecting the recognition, measurement, and presentation of expenses and cash flows arising from a lease. For public entities, the new standard is effective for interim and annual periods beginning on or after January 1, 2019, or January 1, 2020 for non-public entities, with early adoption permitted in each case. The Company is currently evaluating the effect ASU 2016-02 may have on its consolidated financial statements and related disclosures, but expects recognizing the lease liability and related right-of-use asset will impact its consolidated balance sheet.

In July 2018, the FASB issued ASU 2018-07, Compensation—Stock Compensation (Topic 718) (“ASU 2018-07”): Improvements to Nonemployee Share-Based Payment Accounting. ASU 2018-07 aligns the guidance on share-based payments to nonemployees with that for share-based payments to employees. Entities will recognize a cumulative-effect adjustment to retained earnings for equity-classified nonemployee awards for which a measurement date has not been established. The guidance is effective in annual periods beginning after December 31, 2018, and interim periods within those years. Early adoption is permitted for entities that have adopted the new revenue guidance. The Company is currently evaluating the impact that the adoption of ASU 2018-07 will have on its consolidated financial statements.

Shareholders’ Equity

12 Months Ended

Sep. 30, 2018

Equity [Abstract]

Shareholders’ Equity

Ordinary Shares

Each holder of ordinary shares is entitled to one vote per ordinary share and to receive dividends when and if such dividends are recommended by the board of directors and declared by the shareholders. As of September 30, 2018, the Company has not declared any dividends.

As of September 30, 2018, the Company’s authorized capital shares consisted of 200 million ordinary shares with a nominal value of $0.000042 per share.

Initial Public Offering and Impact of Corporate Reorganization

On June 18, 2018, Autolus Therapeutics Limited re-registered as a public limited company and its name was changed from Autolus Therapeutics Limited to Autolus Therapeutics plc (See Note 1).

On June 26, 2018, the Company closed its IPO. In the IPO, the Company sold an aggregate of 10,147,059 ADSs representing the same number of ordinary shares at a public offering price of $17.00 per ADS, which included the full exercise by the underwriters of their option to purchase additional ADSs. Net proceeds were approximately $156.5 million, after deducting underwriting discounts, and commissions and offering expenses paid by the Company of $16.0 million. Upon the closing of the IPO, each separate class of ordinary shares of Autolus Therapeutics plc was converted into a single class of ordinary shares of Autolus Therapeutics plc as described further below.

Prior to the Company’s June 2018 reorganization and IPO, the Company had issued series A preferred shares, ordinary B shares, and ordinary C shares to fund its operations and upon the Company completed its IPO of ADSs, the different classes of shares were converted into a single class of ordinary shares on a 3.185-for-1 basis and created various classes of deferred shares.

The following Deferred shares classes were created:

Deferred Shares - The 34,425 deferred shares, aggregate nominal value less than $1.00, existed in Autolus Limited and were re-created in Autolus Therapeutics plc as part of the share exchange to place Autolus Therapeutics as the ultimate parent entity. The Company was required to replicate the shares to ensure the existing share has the correct nominal value to ensure stamp duty mirroring relief is available on the subsequent share for share exchange. These deferred shares have no voting rights.

Deferred B Shares - The deferred shares were the product of the reorganization of the series A preferred shares and ordinary B shares into ordinary shares. The nominal residual value was utilized by management as the required £50,000 of share capital to re-register Autolus Therapeutics Limited as Autolus Therapeutics plc. The resulting 88,893,548 deferred shares, aggregate nominal value of $118,000, is presented as a separate class of equity on the balance sheet and statement of shareholder’s equity. These deferred B shares have no voting rights.

Deferred C Share - The deferred share, nominal value less than $1.00, was created when the shares in Autolus were redenominated from GBP to USD as part of the capital reduction to deal with rounding issues that would otherwise have unbalanced the company’s nominal share capital. This deferred C share has no voting rights.

The table below reflects the number of preferred, ordinary shares, and deferred issued and outstanding at September 30, 2018, 2017 and 2016, and also reflects the conversion of preferred and ordinary shares on 3.185-for-1 basis in the current and previous years and the creation of deferred shares.



	September 30,
	2018	2017	2016
Series A preferred shares	—	24,490,705	8,994,351
Class B ordinary shares	—	3,375,196	3,375,196
Class C ordinary shares	—	2,096,840	1,551,996
Ordinary Shares	40,146,182	—	—
Deferred shares	34,425	—	—
Deferred B shares	88,893,548	—	—
Deferred C shares	1	—	—
Total Ordinary and Deferred Shares	129,074,156	29,962,741	13,921,543

Share Based Compensation

12 Months Ended

Sep. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Share Based Compensation

In February 2017, the Company’s board of directors adopted the 2017 Share Option Plan, or the 2017 Plan. The 2017 Plan was set to expire on February 21, 2027. The 2017 Plan provided for the grant of potentially tax-favored Enterprise Management Incentives, or EMI, options to the Company's U.K. employees and for the grant of options to its U.S. employees.

In June 2018, as part of the Company's reorganization and IPO, the Company’s board of directors and shareholders approved the 2018 Equity Incentive Plan, or the 2018 Plan. The initial maximum number of ordinary shares that may be issued under the 2018 Plan was 3,281,622. This number consists of 3,025,548 new ordinary shares and 256,074 ordinary shares that would have otherwise remained available for future grants under the 2017 Plan. The number of ordinary shares reserved for issuance under the 2018 Plan will automatically increase on October 1st of each year, for a period of not more than ten years, commencing on October 1, 2018 and ending on (and including) October 1, 2027, by an amount equal to the lesser of (i) 4% of the total number of ordinary shares outstanding on September 30th of the same calendar year or (ii) such fewer number of ordinary shares as the board of directors may designate prior to the applicable October 1st date. Shares issued under the 2018 Plan may be authorized but unissued shares, shares purchased on the open market, treasury shares or ADSs. No more than 14,000,000 shares may be issued under the 2018 Plan upon the exercise of incentive share options.

Options granted under the 2018 Plan and 2017 Plan, as well as restricted shares granted as employee incentives, typically vest over a four-year service period with 25% of the award vesting on the first anniversary of the commencement date and the balance vesting monthly over the remaining three years, unless the award contains specific performance vesting provisions. For equity awards issued that have both a performance vesting condition and a services condition, once the performance criteria is achieved, the awards are then subject to a four-year service vesting with 25% of the award vesting on the first anniversary of the performance condition being achieved and the balance vesting monthly over the remaining three years. Options granted under the 2018 Plan and 2017 Plan generally expire 10 years from the date of grant. For certain senior members of management and directors, the board of directors has approved an alternative vesting schedule.

Share Option Valuation

The assumptions (see Note 2) used in the Black-Scholes option pricing model to determine the fair value of the share options granted to employees and directors during the year ended September 30, 2018 and 2017 were as follows:



	September 30,
	2018	2017
Expected option life (years)	6 years	6 years
Risk-free interest rate	2.61% to 3.00%	1.91% to 2.05%
Expected volatility	68.15% to 72.99%	68.61% to 68.93%
Expected dividend yield	0.00%	0.00%

Share Options

The table below reflects the conversion of ordinary shares in the current and previous years.



	Number of Options		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding as of September 30, 2016	—		$	—	—	$	—
Granted	570,537		0.51		—	—
Exercised	—		—		—	—
Canceled or forfeited	(228	)	0.00		—	—
Outstanding as of September 30, 2017	570,309		$	0.51	9.73	$	2,024
Granted	1,513,218		$	13.33	—	—
Exercised	—		—		—	—
Canceled or forfeited	(18,046	)	$	4.99	—	—
Outstanding as of September 30, 2018	2,065,481		$	9.87	9.35	$	43,146
Exercisable as of September 30, 2018	166,262		$	0.52	8.73	$	5,022
Vested and expected to vest as of September 30, 2018	2,065,481		$	9.87	9.35	$	43,146

The aggregate intrinsic value of share options is calculated as the difference between the exercise price of the share options and the fair value of the Company’s restricted ordinary shares for those share options that had exercise prices lower than the fair value of the Company’s restricted ordinary shares.

The weighted average grant-date fair value of share options granted during the year ended September 30, 2018 and 2017 was $8.55 and $4.04 per share, respectively, none of which were vested. There were no share options granted during the year ended September 30, 2016.

The Company granted 570,537 share options during the year ended September 30, 2017 of which 556,966 were performance-based share options. These performance-based share options begin to vest upon the Company achieving specified clinical development milestones. During the year ended September 30, 2017, 228 of the performance-based share options were forfeited. There were no performance-based share options granted during the year ended September 30, 2018.

The Company achieved the milestones related to the 2017 performance-based share options during the year ended September 30, 2017 and recorded share-based compensation expense of $1.0 million and $0.4 million related to those option awards that started vesting upon the achievement of the milestones for the years ended September 30, 2018 and 2017, respectively. As of September 30, 2018, there was unrecognized compensation of $0.6 million related to the 2017 performance-based share options, which will be recognized over the remaining term of the awards.

The Company recorded share-based compensation expense related to share options to certain consultants, who are not employees, of $0.1 million for the year ended September 30, 2018. There were no share options granted to consultants during the year ended September 30, 2017.

Restricted Ordinary Shares

The assumptions (Note 2) used in the OPM to determine the fair value of the ordinary shares for the following dates are as follows:



	March 2, 2016		April 26, 2017		September 25, 2017		March 31, 2018		May 31, 2018
Expected term	2.8 years		1.2 years		0.8 years		1.8 years		1.8 years
Risk-free interest rate	1.0	%	1.0	%	1.3	%	2.1	%	2.1	%
Expected volatility	73.2	%	76.6	%	71.0	%	71	%	71	%
Expected dividend yield	0.0	%	0.0	%	0.0	%	0.0	%	0.0	%

A summary of the changes in the Company’s restricted ordinary shares during the years ended September 30, 2018 and 2017 are as follows and reflect the conversion of ordinary shares in the current and previous years.



	Number of restricted shares		Weighted average grant date fair value
Unvested and outstanding at September 30, 2015	416,887		$	3.54
Granted	1,070,797		4.08
Vested	(220,940	)	3.38
Canceled or forfeited	(125	)	3.03
Unvested and outstanding at September 30, 2016	1,266,619		3.89
Granted	642,150		4.36
Vested	(453,134	)	3.92
Canceled or forfeited	(97,318	)	4.20
Unvested and outstanding at September 30, 2017	1,358,317		4.20
Granted	—		—
Vested	(534,906	)	3.96
Canceled or forfeited	(7,779	)	3.68
Unvested and outstanding at September 30, 2018	815,632		$	4.17

During the year ended September 30, 2017, the Company granted an aggregate of 439 restricted ordinary shares with vesting based on service conditions only and 641,711 restricted ordinary shares that included both performance and service conditions in order to vest. During the years ended September 30, 2018 and 2017, 159,490 and 24,896 restricted ordinary shares were vested related to performance-based awards. The remainder of the restricted C ordinary shares and all forfeited restricted C ordinary shares related to awards with only service-based vesting conditions. There were no restricted shares granted during the year ended September 30, 2018.

The 2017 performance-based restricted shares were scheduled to begin vesting upon the Company’s achievement of specified clinical development milestones. The Company achieved the milestones related to the 2017 performance-based restricted shares during the year ended September 30, 2017 and recorded share-based compensation expense of $1.0 million and $0.8 million related to the vesting of those incentive share awards for the years ended September 30, 2018 and 2017, respectively.

As of September 30, 2018, there was unrecognized compensation of $0.8 million, which will be recognized over the remaining vesting term of the awards.

The Company recorded share-based compensation expense related to awards to certain consultants, who are not employees, of $1.0 million and $0.2 million for the years ended September 30, 2018 and 2017, respectively.

Share-based Compensation Expense

The Company recorded share-based compensation expense of $6.8 million and $3.2 million during the years ended September 30, 2018 and 2017, respectively, related to both restricted shares and share options based awards. As of September 30, 2018, there was $12.2 million of unrecognized compensation cost related to outstanding but unvested restricted shares and share options, which amounts are expected to be recognized over weighted-average period of 3.5 years.

Share-based compensation expense recorded as research and development and general and administrative expenses is as follows (in thousands):



	Year ended September 30,
	2018		2017		2016
Research and development	$	3,116	$	1,145	$	916
General and administrative	3,649		2,008		1,341
Total share-based compensation	$	6,765	$	3,153	$	2,257

In February 2017, the Company modified the terms of all outstanding share options and restricted share awards to adjust the vesting of the awards in the event of an exit event or IPO. As modified, the options and share awards do not convert to deferred shares and will continue vesting as a result of the June 2018 IPO. The incremental share-based compensation expense due to the modification was nominal.

License Agreements	12 Months Ended
License Agreements	Sep. 30, 2018
License Agreements [Abstract]
License Agreements	License Agreements UCL Business plc License In September 2014, the Company entered into an exclusive license agreement (the “License”) with UCLB, to obtain licenses to certain technology rights in the field of cancer therapy and diagnosis. In March 2016, the License was amended to include additional rights. As part of the consideration for the License in September 2014, the Company issued 1,497,643 ordinary shares to UCLB. The Company paid upfront fees of $0.3 million and issued an additional 313,971 ordinary shares to UCLB when the License was amended in March 2016. In March 2018, the License was further amended and restated in March 2018 to include a license to AUTO1, for which UCL is conducting Phase 1 clinical trials in pediatric and adult ALL patients. The Company paid an upfront fee of £1.5 million for consideration for the Amended and Restated License Agreement and are obligated to pay an additional £0.5 million in connection with UCLB's transfer of clinical data to the Company. No equity was issued as part of the upfront fee consideration. The License requires the Company to make annual license payments of £30,000 through the year ending September 30, 2018. Additionally, the Company may be obligated to make payments to UCLB under the Amended and Restated License Agreement upon the receipt of specified regulatory approvals in an aggregate amount of £35.5 million, the start of commercialization in an aggregate amount of £18 million, and the achievement of net sales levels in an aggregate amount of £51 million, as well as royalty payments based on possible future sales resulting from the utilization of the licensed technologies. On a per-product basis, these milestone payments range from £1 million to £18.5 million, depending on which T cell programming modules are used in the product achieving the milestone. Upon commercialization of any of the Company’s products that use the in-licensed patent rights, the Company will be obligated to pay UCLB a flat royalty for each licensed product ranging from the low- to mid-single digits, depending on which technologies are deployed in the licensed product, based on worldwide annual net sales of each licensed product, subject to certain reductions, including for the market entry of competing products and for loss of patent coverage of licensed products. The Company may deduct from the royalties payable to UCLB half of any payments made to a third party to obtain a license to such third party’s intellectual property that is necessary to exploit any licensed products. Once net sales of a licensed product have reached a certain specified threshold, the Company may exercise an option to buy out UCLB’s rights to the remaining milestone payments, royalty payments, and sublicensing revenue payments for such licensed product, on terms to be negotiated at the time. The License expires on a product-by-product and country-by-country basis upon the expiration of the royalty term with respect to each product in each country. The Company may unilaterally terminate the license agreement for any reason upon advance notice to UCLB. Either party may terminate the License for the uncured material breach by the other party or for the insolvency of the other party. If UCLB terminates the License following the Company’s insolvency or the Company’s material breach of the License, or if the Company terminates the License unilaterally, all rights and licenses granted to the Company will terminate, and all patent rights and know-how transferred to the Company pursuant to the License will revert back to UCLB, unless and to the extent the Company has exercised its option to acquire ownership of the licensed patent rights. In addition, UCLB has the right to negotiate with the Company for the grant of an exclusive license to the Company’s improvements to the T cell programming modules the Company has licensed on terms to be agreed upon at the time.

Income Taxes

12 Months Ended

Sep. 30, 2018

Income Tax Disclosure [Abstract]

Income Taxes

The Company recorded an income tax benefit of $7.3 million and $3.7 million for the years ended September 30, 2018 and 2017, respectively.

A reconciliation of income tax expense (benefit) at the statutory corporate income tax rate to the income tax expense (benefit) at the Company’s effective income tax rates is as follows (in thousands):



	September 30,
	2018			2017			2016
Net loss before taxes	$	(52,031	)	$	(23,380	)	(14,327		)
U.K. statutory tax rate	19.0		%	19.5		%	20		%
Income tax benefit at U.K. statutory tax rate	(9,886		)	(4,559		)	(2,865		)
Tax incentives / credits	(7,296		)	(3,702		)	(1,837		)
Non-deductible expenses	1,553			609			694
Adjustments in respect of prior years	(13		)	13			57
Operating losses	7,317			3,754			2,168
Tax on property, plant, equipment and intangibles	233			113			—
Other, net	812			119			6
Total income tax benefit	$	(7,280	)	$	(3,653	)	$	(1,777	)
Effective rate of income tax	14.0		%	15.6		%	12.4		%

The effective tax rate for September 30, 2018, 2017, and 2016 is 14%, 15.6% and 12.4%, respectively. This is lower than the main rate of U.K. tax primarily due to administration of the U.K. research and development tax credit, which is included within the tax incentive/credits line in the table above.

Deferred tax assets and liabilities consisted of the following at September 30, 2018 and 2017 (in thousands):



	September 30,
	2018			2017
Deferred tax assets:
Other differences	$	1,785		$	11
Tax losses	6,515			3,878
Fixed assets	10,233			1,098
Total deferred tax assets	18,533			4,987
Valuation allowances	(18,533		)	(4,987		)
Net deferred tax asset (liability)	$	—		$	—

Deferred tax assets resulting from loss carryforwards, fixed assets and retirement benefits, with total deferred tax assets increasing by $13.5 million in 2018. The Company has recorded a full valuation allowance against the net deferred tax asset as the recoverability due to future taxable profits is unknown. As a result, the net deferred tax remains the same, due to a corresponding increase in valuation allowance.

At September 30, 2018, the Company had U.K. trading losses carry forward of approximately $38.0 million. These losses are carry forwards indefinitely under local law, but are subject to numerous utilization criteria and restrictions.

As required by the authoritative guidance on accounting for income taxes, the Company evaluates the realizability of deferred tax assets at each reporting date. Accounting for income taxes guidance requires that a valuation allowance be established when it is more likely than not that all or a portion of the deferred tax assets will not be realized. In circumstances where this is sufficient negative evidence indicating that the deferred tax assets are not more likely than not realizable, the Company establishes a valuation allowance. The Company recorded valuation allowances in the amounts of $18.5 million and $5.0 million at September 30, 2018 and 2017, respectively.

Commitments and Contingencies

12 Months Ended

Sep. 30, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

License Agreement

The Company has entered into an exclusive license agreement, as amended, with UCLB (see Note 8). In connection with the UCLB license agreement, the Company is required to make annual license payments and may be required to make payments upon the achievement of specified milestones. The Company has estimated the probability of the Company achieving each potential milestone in accordance with ASC 450, Contingencies. The Company concluded that, as of September 30, 2018 there was a $0.7 million milestone that was considered probable related to the receipt of clinical data for its AUTO1 program, and accordingly the Company has accrued a liability of $0.7 million as of September 30, 2018. As of September 30, 2017, there were no other milestones for which the likelihood of achievement was probable.

Legal Proceedings

From time to time, the Company may be a party to litigation or subject to claims incident to the ordinary course of business. Regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources and other factors. The Company was not a party to any litigation and did not have contingency reserves established for any liabilities as of September 30, 2018 and 2017.

Leases

The Company’s corporate headquarters are located in London, United Kingdom. As of September 30, 2018 and 2017, the Company leased space at this location from Imperial (Forest House) Limited under a ten year lease, the term of which commenced in September 2015. The lease included an option for the Company to lease additional space within a 15-month period, which the Company exercised in October 2016. The exercise of the option resulted in a separate new lease with a concurrent term through August 2025. The Company and the landlord has the option to early terminate both leases in September 2020.

Prior to the lease commencement date of both leases, the Company, in conjunction with the landlord, made improvements to the leased space. The total cost of these improvements was funded by the landlord, a portion of the cost will be reimbursed by the Company over the term of the leases. The total cost of the improvements was capitalized as leasehold improvements on the Company’s balance sheet, with an offset to long-term lease incentive obligation for the portion funded by the landlord and other long-term payables for the portion to be repaid to the landlord. As of September 30, 2018 and 2017, the Company capitalized $0.1 million and $2.1 million, respectively, as leasehold improvements. The lease related to this facility is classified as an operating lease.

In September 2017, the Company executed a lease arrangement with Catapult Limited to lease manufacturing space for a term through May 15, 2021, at which time the Company has the option to renew or terminate the lease. The lease related to this facility is classified as an operating lease. The lease has an eight-month rent-free period. The rent-free period is included in the deferred rent.

In June 2018, the Company signed a binding letter of intent to enter into a lease with Whitewood Media Village GP Limited and Whitewood Media Village Nominee Limited. The future lease will require the Company to enter into an eight years lease and is dependent on the landlord completing the required leasehold improvements per the agreement to execute the lease. The expected lease commencement date is in November 2018. The lease will include an option to lease additional space. As of September 30, 2018, the Company capitalized $2.5 million as leasehold improvements. The Company did not include future minimum payments in the lease payment schedule, as the lease agreement is not complete as of September 30, 2018.

In September 2018, the Company signed a binding letter of intent to enter into a lease with The Royal London Mutual Insurance Society Limited. The future lease will require the Company to enter into a 15 year lease and is dependent on the landlord completing the required leasehold improvements per the agreement to execute the lease. The expected lease commencement date is in November 2018. The Company has incurred no leasehold improvements to capitalize as of September 30, 2018. The Company did not include future minimum payments in the lease payment schedule as the lease agreement is not complete as of September 30, 2018.

The following table summarizes the future minimum lease payments due under operating leases as of September 30, 2018 (in thousands):



Year ending September 30,
2019	$	1,316
2020	1,382
2021	1,017
2022	1,070
2023	1,037
Thereafter	1,300
Total	$	7,122

The Company recognizes rent expense on a straight-line basis over the respective lease period and has recorded deferred rent for rent expense incurred but not yet paid.

The Company recorded rent expense totaling $0.9 million and $0.6 million for the years ended September 30, 2018 and 2017, respectively.

Related Party Transactions	12 Months Ended
Related Party Transactions	Sep. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Syncona LLP The Company has an agreement with Syncona LLP, investor in the Company, pursuant to which the Company is charged for services including director compensation fees. The Company recorded expenses totaling $60,000 $56,000, and $0.2 million for the years ended September 30, 2018, 2017, and 2016, respectively, which are included in general and administrative expenses. As of September 30, 2018 and 2017 there was $13,000 and $3,000 included in accrued expenses on the Company’s balance sheets related to the arrangement with Syncona LLP, respectively. University College London and Related Entities Prior to September 30, 2018, UCL is no longer a principal shareholder of the Company and, as a result, the Company no longer considers UCL a related party for reporting purposes. Prior to September 30, 2018, the Company recorded research and development expenses totaling $0.7 million and $2.4 million, of which $40,000 and $1.5 million represent license fees for the years ended September 30, 2017 and 2016, respectively. The Company, under various agreements, receives research and development, office and consulting services from the University College London and its subsidiaries. The UCL is a shareholder of the Company through UCLB. As of September 30, 2017 and 2016, there was $0.2 million and $43,000, respectively, of which is included in accrued expenses and accounts payable on the Company’s balance sheets related to the arrangement with the University College London. The Wellcome Trust The Company has an arrangement with The Wellcome Trust, previously the holding company of Syncona LLP, pursuant to which the Company is billed for certain administrative and consulting services. There were nominal charges for the years ended September 30, 2017 for processing of salaries from The Wellcome Trust. There was no activity for the years ended September 30, 2018. As of September 30, 2018 and 2017, there were no unpaid amounts related to this arrangement that were included in accrued expenses on the Company’s balance sheets. Arix Bioscience The Company has an agreement with Arix Bioscience Holdings Limited, investor of the Company, pursuant to which, the Company is charged for director compensation fees. The Company recorded expenses totaling $18,000, $20,000, and $11,000 for the years ended September 30, 2018, 2017, and 2016, respectively. As of September 30, 2018 there was no outstanding balance and ,as of September 30, 2017, there was $2,000 included in accrued expenses on the Company’s balance sheets. There was no outstanding balance as of September 30, 2018. Kapil Dhingra, M.D., The Company entered into a consulting agreement with Dr. Kapil Dhingra, a member of its board of directors, in November 2014, pursuant to which he has agreed to provide up to nine days of healthcare consulting services to the Company. Dr. Dhingra receives an annual fee of £10,000 under the terms of the agreement. Subject to mutual agreement between the Company and Dr. Dhingra, he may provide services to the Company beyond the nine days, in which case the Company has agreed to pay Dr. Dhingra an additional fee of £1,111 per day. As of September 30, 2018 and 2017, there was $46,000 and $32,000 included in accrued expenses on the Company’s balance sheets.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include those of the Company, Autolus Limited, and its U.S. subsidiary, Autolus Inc., and have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). All intercompany accounts and transactions have been eliminated upon consolidation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of income and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the accrual for research and development expenses, the fair value of ordinary shares, the valuation of tranche obligations, share-based compensation and income taxes. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ materially from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments that have maturities of three months or less when acquired to be cash equivalents.
Fair Value Measurements	Fair Value Measurements The carrying amounts reported in the balance sheets for cash, prepaid expenses and other assets, accounts payable and accrued expenses and other liabilities approximate their fair value because of the short-term nature of these instruments.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that subject the Company to credit risk consist primarily of cash and cash equivalents. The Company places cash and cash equivalents in established financial institutions. The Company has no significant off-balance-sheet risk or concentration of credit risk, such as foreign exchange contracts, options contracts, or other foreign hedging arrangements.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost and depreciated or amortized using the straight-line method over the estimated useful lives of the respective assets. As of September 30, 2018 and 2017, the Company’s property and equipment consisted of office equipment, lab equipment, furniture and fixtures, and leasehold improvements. The office equipment has an estimated useful life of three years and the lab equipment and furniture and fixtures have an estimated useful life of five years. Leasehold improvements are depreciated over the shorter of the lease term or the estimated useful life of the asset. Assets under construction consist of costs incurred with leasehold improvements and, once placed into service, will be depreciated over the shorter of the lease term or the estimated useful life of the asset. Upon retirement or sale, the cost of assets disposed of, and the related accumulated depreciation, are removed from the accounts and any resulting gain or loss is included in the statement of operations and other comprehensive loss. Repairs and maintenance expenditures, which are not considered improvements and do not extend the useful life of property and equipment, are expensed as incurred. The Company evaluates an asset for potential impairment when events or changes in circumstances indicate the carrying value of the asset may not be recoverable. Recoverability is measured by comparing the book value of the asset to the expected future net undiscounted cash flows that the asset is expected to generate. If such asset is considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the asset exceeds the fair value. The Company has not recognized any impairment losses from its inception through September 30, 2017.
Intangible Assets Subject to Amortization	Intangible Assets Subject to Amortization The Company’s intangible assets with finite lives are amortized over their useful lives and reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. If any indicators were present, the Company would test for recoverability by comparing the carrying amount of the asset to the net undiscounted cash flows expected to be generated from the asset. If those net undiscounted cash flows do not exceed the carrying amount (i.e., the asset is not recoverable), the Company would perform the next step, which is to determine the fair value of the asset and record an impairment loss, if any. The Company evaluates the useful lives for these intangible assets each reporting period to determine whether events and circumstances warrant a revision in their remaining useful lives. The Company’s intangible assets are not available for use and therefore no amortization has been charged to date.
Segment Information	Segment Information Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker in deciding how to allocate resources and assess performance. The Company and the Company’s chief operating decision maker, the Company’s Chief Executive Officer, view the Company’s operations and manages its business as a single operating segment, which is the business of developing and commercializing gene therapies; however, the Company operates in two geographic regions:
Deferred Rent and Lease Incentive	Deferred Rent and Lease Incentives Rent expense and lease incentives from operating leases are recognized on a straight-line basis over the lease term. The Company has operating leases that include rent escalation payment terms and a rent free period. Deferred rent represents the difference between actual operating lease payments and straight-line rent expense over the term of the lease.
Research and Development Costs	Accrued Research and Development Expenses As part of the process of preparing consolidated financial statements, the Company is required to estimate accruals for research and development expenses. This process involves reviewing and identifying services which have been performed by third parties on the Company’s behalf and determining the value of these services. In addition, the Company makes estimates of costs incurred to date but not yet invoiced, in relation to external CROs and clinical site costs. The Company analyzes the progress of clinical trials, including levels of patient enrollment; invoices received and contracted costs, when evaluating the adequacy of the accrued liabilities for research and development. The Company makes judgments and estimates in determining the accrued balance in any accounting period. Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities, including salaries, share-based compensation and benefits, depreciation expense, third-party license fees, external costs of outside vendors engaged to conduct clinical development activities, clinical trials, costs to manufacture clinical trial materials and certain tax credits associated with research and development activities.
Share-based Compensation	Share-Based Compensation The Company recognizes compensation expense for equity awards based on the grant date fair value of the award. The Company recognizes share-based compensation expense for awards granted to employees that have a graded vesting schedule based on a service condition only on a straight-line basis over the requisite service period for each separately vesting portion of the award as if the award was, in substance, multiple awards (the “graded-vesting attribution method”), based on the estimated grant date fair value for each separately vesting tranche. For equity awards with a graded vesting schedule and a combination of service and performance conditions, the Company recognizes share-based compensation expense using a graded-vesting attribution method over the requisite service period when the achievement of a performance-based milestone is probable, based on the relative satisfaction of the performance condition as of the reporting date. For share-based awards granted to consultants and non-employees, compensation expense is recognized using the graded-vesting attribution method over the period during which services are rendered by such consultants and non-employees until completed. At the end of each financial reporting period prior to completion of the service, the fair value of these awards is remeasured using the then-current fair value of the Company’s ordinary shares. The Company accounts for forfeitures as they occur. Forfeitures to date have been infrequent and immaterial. The fair value of each share option grant is estimated on the date of grant using the Black-Scholes option pricing model. See Note 7 for the Company’s assumptions used in connection with option grants made during the periods covered by these financial statements. Assumptions used in the option pricing model include the following: Expected volatility. The Company lacks company-specific historical and implied volatility information for its ADSs. Therefore, the Company estimates the expected share volatility based on the historical volatility of publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded share price. Expected term. The expected term of the Company’s share options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. Risk-free interest rate. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods that are approximately equal to the expected term of the award. Expected dividend. Expected dividend yield of zero is based on the fact that the Company has never paid cash dividends on ordinary shares and does not expect to pay any cash dividends in the foreseeable future. Fair value of ordinary shares. Options granted after the Company’s IPO are issued at the fair market value of the Company’s ADS at the date the grant is approved by the Board. Prior to the IPO, the Company calculated the fair value of its ordinary shares in accordance with the guidelines in the American Institute of Certified Public Accountants’ Accounting and Valuation Guide, Valuation of Privately-Held-Company Equity Securities Issued as Compensation. The Company’s valuations of ordinary shares were prepared using a market approach, based on precedent transactions in the shares, to estimate the Company’s total equity value using the option-pricing method (“OPM”), which used a combination of market approaches and an income approach to estimate the Company’s enterprise value. The OPM derives an equity value such that the value indicated is consistent with the investment price, and it provides an allocation of this equity value to each class of the Company’s securities. The OPM treats the various classes of shares as call options on the total equity value of a company, with exercise prices based on the value thresholds at which the allocation among the various holders of a company’s securities changes. Under this method, each class of shares has value only if the funds available for distribution to shareholders exceed the value of the share liquidation preferences of the class or classes of shares with senior preferences at the time of the liquidity event. Key inputs and assumptions used in the OPM calculation include the following: Expected volatility. The Company applied re-levered equity volatility based on the historical unlevered and re-levered equity volatility of publicly traded peer companies. Expected dividend. Expected dividend yield of zero is based on the fact that the Company has never paid cash dividends on ordinary shares and does not expect to pay any cash dividends in the foreseeable future. Expected term. The expected term of the option or the estimated time until a liquidation event. Risk-free interest rate. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve for the period commensurate with the expected of the exit event.
Foreign Currency Translation	Foreign Currency Translation The Company maintains its financial statements in its functional currency, which is the pounds sterling. Monetary assets and liabilities denominated in currencies other than the functional currency are translated into the functional currency at rates of exchange prevailing at the balance sheet dates. Non-monetary assets and liabilities denominated in foreign currencies are translated into the functional currency at the exchange rates prevailing at the date of the transaction. Exchange gains or losses arising from foreign currency transactions are included in the determination of net income (loss) for the respective periods. The Company recorded foreign exchange gain of $4.0 million and and foreign exchange loss of $25,000 for the years ended September 30, 2018 and 2017, respectively, which are included in other income in the statements of operations and comprehensive loss. For financial reporting purposes, the financial statements of the Company have been translated into U.S. dollars. Assets and liabilities have been translated at the exchange rates at the balance sheet dates, while revenue and expenses are translated at the average exchange rates over the reporting period and shareholders’ equity amounts are translated based on historical exchange rates as of the date of each transaction. Translation adjustments are not included in determining net income (loss) but are included in foreign exchange adjustment to other comprehensive loss, a component of shareholders’ equity.
Patent Costs	Patent Costs The Company expenses patent prosecution and related legal costs as they are incurred and classifies such costs as general and administrative expenses in the accompanying statements of operations and comprehensive loss.
Grant Income	Grant Income The Company has received research grants under which it is reimbursed for specific research and development activities. Payments received are recognized as income in the statements of operations and comprehensive loss over the period in which the Company recognizes the related costs. At the time the Company recognizes grant income, it has complied with the conditions attached to it and the receipt of the reimbursement is reasonably assured. The Company has received grants from the U.K. government, which are repayable under certain circumstances, including breach or noncompliance. For grants with refund provisions, the Company reviews the grant to determine the likelihood of repayment. If the likelihood of repayment of the grant is determined to be remote, then the grant is recognized as grant income. The Company has determined that the likelihood of any repayment events included in its current grants is remote.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method which includes the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s financial statements. Under this approach, deferred taxes are recorded for the future tax consequences expected to occur when the reported amounts of assets and liabilities are recovered or paid. The provision for income taxes represents income taxes paid or payable for the current year plus deferred taxes. Deferred taxes result from differences between the financial statements and tax bases of the Company’s assets and liabilities, and are adjusted for changes in tax rates and tax law when changes are enacted. The effects of future changes in income tax laws or rates are not anticipated. The Company is subject to income taxes in the United Kingdom and the United States. The calculation of the Company’s tax provision involves the application of United Kingdom tax law and requires judgement and estimates. The Company evaluates the realizability of its deferred tax assets at each reporting date, and establishes a valuation allowance when it is more likely than not that all or a portion of its deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income of the same character and in the same jurisdiction. The Company considers all available positive and negative evidence in making this assessment, including, but not limited to, the scheduled reversal of deferred tax liabilities, projected future taxable income, and tax planning strategies. In circumstances where there is sufficient negative evidence indicating that the Company’s deferred tax assets are not more likely than not realizable, the Company establishes a valuation allowance. The Company uses a two-step approach for recognizing and measuring uncertain tax positions. The first step is to evaluate tax positions taken or expected to be taken in a tax return by assessing whether they are more likely than not sustainable, based solely on their technical merits, upon examination, and including resolution of any related appeals or litigation process. The second step is to measure the associated tax benefit or each position as the largest amount that the Company believes is more likely than not realizable. Differences between the amount of tax benefits taken or expected to be taken in the Company’s income tax returns and the amount of tax benefits recognized in the its financial statements represent the Company’s unrecognized income tax benefits, which it either records as a liability or reduction of deferred tax assets. Income Tax Credit The Company benefits from the U.K. research and development tax credit regime under both the small and medium sized enterprise, or SME, scheme and by claiming an RDEC in respect of grant funded projects. Under the SME regime, a portion of the Company’s losses can be surrendered for a cash rebate of up to 33.35% of eligible expenditures. Such credits are accounted for within the tax provision in the year in which the expenditures were incurred.
Comprehensive Loss	Comprehensive Loss The Company follows the provisions of the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 220, Comprehensive Income, which establishes standards for the reporting and display of comprehensive income and its components. Comprehensive loss is defined to include all changes in equity during a period except those resulting from investments by owners and distributions to owners.
Net Loss per Share	Net Loss per Share Basic and diluted net loss per ordinary share is determined by dividing net loss by the weighted average number of ordinary shares outstanding during the period. For all periods presented, the preferred shares and outstanding but unvested restricted shares and share options have been excluded from the calculation, because their effects would be anti-dilutive. Therefore, the weighted average shares outstanding used to calculate both basic and diluted loss per share are the same for all periods presented.
Recent Accounting Pronouncements	Recently issued accounting pronouncements not yet adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”), which requires a lessee to recognize certain leases on the balance sheet but recognize expenses on the income statement in a manner similar to current accounting standards practice. The update states that a lessee will recognize a lease liability for the obligation to make lease payments and a right-to-use asset for the right to use the underlying assets for the lease term. Leases will continue to be classified as either financing or operating, with classification affecting the recognition, measurement, and presentation of expenses and cash flows arising from a lease. For public entities, the new standard is effective for interim and annual periods beginning on or after January 1, 2019, or January 1, 2020 for non-public entities, with early adoption permitted in each case. The Company is currently evaluating the effect ASU 2016-02 may have on its consolidated financial statements and related disclosures, but expects recognizing the lease liability and related right-of-use asset will impact its consolidated balance sheet. In July 2018, the FASB issued ASU 2018-07, Compensation—Stock Compensation (Topic 718) (“ASU 2018-07”): Improvements to Nonemployee Share-Based Payment Accounting. ASU 2018-07 aligns the guidance on share-based payments to nonemployees with that for share-based payments to employees. Entities will recognize a cumulative-effect adjustment to retained earnings for equity-classified nonemployee awards for which a measurement date has not been established. The guidance is effective in annual periods beginning after December 31, 2018, and interim periods within those years. Early adoption is permitted for entities that have adopted the new revenue guidance. The Company is currently evaluating the impact that the adoption of ASU 2018-07 will have on its consolidated financial statements.

Shareholders’ Equity (Tables)

12 Months Ended

Sep. 30, 2018

Equity [Abstract]

Schedule of Shares Outstanding



	September 30,
	2018	2017	2016
Series A preferred shares	—	24,490,705	8,994,351
Class B ordinary shares	—	3,375,196	3,375,196
Class C ordinary shares	—	2,096,840	1,551,996
Ordinary Shares	40,146,182	—	—
Deferred shares	34,425	—	—
Deferred B shares	88,893,548	—	—
Deferred C shares	1	—	—
Total Ordinary and Deferred Shares	129,074,156	29,962,741	13,921,543

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

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Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
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+ Details

Share Based Compensation (Tables)

12 Months Ended

Sep. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Stock Options Valuation Assumptions



	September 30,
	2018	2017
Expected option life (years)	6 years	6 years
Risk-free interest rate	2.61% to 3.00%	1.91% to 2.05%
Expected volatility	68.15% to 72.99%	68.61% to 68.93%
Expected dividend yield	0.00%	0.00%

Stock Option Rollforward

The table below reflects the conversion of ordinary shares in the current and previous years.



	Number of Options		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding as of September 30, 2016	—		$	—	—	$	—
Granted	570,537		0.51		—	—
Exercised	—		—		—	—
Canceled or forfeited	(228	)	0.00		—	—
Outstanding as of September 30, 2017	570,309		$	0.51	9.73	$	2,024
Granted	1,513,218		$	13.33	—	—
Exercised	—		—		—	—
Canceled or forfeited	(18,046	)	$	4.99	—	—
Outstanding as of September 30, 2018	2,065,481		$	9.87	9.35	$	43,146
Exercisable as of September 30, 2018	166,262		$	0.52	8.73	$	5,022
Vested and expected to vest as of September 30, 2018	2,065,481		$	9.87	9.35	$	43,146

Schedule of Nonvested Share Activity



	Number of restricted shares		Weighted average grant date fair value
Unvested and outstanding at September 30, 2015	416,887		$	3.54
Granted	1,070,797		4.08
Vested	(220,940	)	3.38
Canceled or forfeited	(125	)	3.03
Unvested and outstanding at September 30, 2016	1,266,619		3.89
Granted	642,150		4.36
Vested	(453,134	)	3.92
Canceled or forfeited	(97,318	)	4.20
Unvested and outstanding at September 30, 2017	1,358,317		4.20
Granted	—		—
Vested	(534,906	)	3.96
Canceled or forfeited	(7,779	)	3.68
Unvested and outstanding at September 30, 2018	815,632		$	4.17

Schedule of Restricted Stock Valuation Assumptions

The assumptions (Note 2) used in the OPM to determine the fair value of the ordinary shares for the following dates are as follows:



	March 2, 2016		April 26, 2017		September 25, 2017		March 31, 2018		May 31, 2018
Expected term	2.8 years		1.2 years		0.8 years		1.8 years		1.8 years
Risk-free interest rate	1.0	%	1.0	%	1.3	%	2.1	%	2.1	%
Expected volatility	73.2	%	76.6	%	71.0	%	71	%	71	%
Expected dividend yield	0.0	%	0.0	%	0.0	%	0.0	%	0.0	%

Schedule of Allocated Share Based Compensation

Share-based compensation expense recorded as research and development and general and administrative expenses is as follows (in thousands):



	Year ended September 30,
	2018		2017		2016
Research and development	$	3,116	$	1,145	$	916
General and administrative	3,649		2,008		1,341
Total share-based compensation	$	6,765	$	3,153	$	2,257

Income Taxes (Tables)

12 Months Ended

Sep. 30, 2018

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of Income Tax Expense (Benefit)



	September 30,
	2018			2017			2016
Net loss before taxes	$	(52,031	)	$	(23,380	)	(14,327		)
U.K. statutory tax rate	19.0		%	19.5		%	20		%
Income tax benefit at U.K. statutory tax rate	(9,886		)	(4,559		)	(2,865		)
Tax incentives / credits	(7,296		)	(3,702		)	(1,837		)
Non-deductible expenses	1,553			609			694
Adjustments in respect of prior years	(13		)	13			57
Operating losses	7,317			3,754			2,168
Tax on property, plant, equipment and intangibles	233			113			—
Other, net	812			119			6
Total income tax benefit	$	(7,280	)	$	(3,653	)	$	(1,777	)
Effective rate of income tax	14.0		%	15.6		%	12.4		%

Schedule of Deferred Tax Assets and Liabilities

Deferred tax assets and liabilities consisted of the following at September 30, 2018 and 2017 (in thousands):



	September 30,
	2018			2017
Deferred tax assets:
Other differences	$	1,785		$	11
Tax losses	6,515			3,878
Fixed assets	10,233			1,098
Total deferred tax assets	18,533			4,987
Valuation allowances	(18,533		)	(4,987		)
Net deferred tax asset (liability)	$	—		$	—

Nature of the Business (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	Jun. 26, 2018 $ / shares shares	Jun. 22, 2018 USD ($)	Sep. 30, 2018 USD ($) $ / shares	Sep. 30, 2017 USD ($) $ / shares	Sep. 30, 2016 USD ($)	Jun. 22, 2018 £ / shares	Jun. 22, 2018 $ / shares	Sep. 30, 2015 USD ($)
Class of Stock
Equity conversion ratio		3.185
Net loss			$ 44,751	$ 19,727	$ 12,550
Accumulated deficit			92,653	47,902
Cash			$ 247,089	$ 137,070	$ 28,059			$ 10,203
Ordinary shares
Class of Stock
Common stock, par value (usd/gbp per share) \| (per share)			$ 0.000042	$ 0.000042		£ 0.000032	$ 0.000042
Ordinary shares \| IPO
Class of Stock
Number of shares issued in transaction (shares) \| shares	10,147,059
Per share price of issuance (usd per share) \| $ / shares	$ 17.00
Proceeds of issuance of ordinary shares, net of issuance costs		$ 156,500
Ordinary shares \| Options
Class of Stock
Number of shares issued in transaction (shares) \| shares	1,323,529

Summary of Significant Accounting Policies - Property and Equipment (Details) - USD ($)	12 Months Ended	39 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment
Fixed asset impairment	$ 10,000	$ 0
Office equipment
Property, Plant and Equipment
Property, plant and equipment useful life	3 years
Lab equipment
Property, Plant and Equipment
Property, plant and equipment useful life	5 years
Furniture and fixtures
Property, Plant and Equipment
Property, plant and equipment useful life	5 years

Summary of Significant Accounting Policies - Schedule of Anti-dilutive Shares (Details) - shares	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares (shares)	2,881,113	1,928,626	1,266,619
Unvested restricted incentive shares
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares (shares)	815,632	1,358,317	1,266,619
Incentive share options
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares (shares)	2,065,481	570,309	0

Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Research and development claims receivable	$ 7,191	$ 4,069
Prepayments	2,208	681
VAT receivable	1,274	248
Other asset	717	0
Grant income receivable	678	279
Other receivable	121	135
Total prepaid expenses and other current assets	$ 12,189	$ 5,412

Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment
Less: accumulated depreciation	$ (3,138)	$ (1,528)
Property, Plant and Equipment, Net	13,528	6,180
Lab equipment
Property, Plant and Equipment
Property and equipment, gross	10,473	4,141
Office equipment
Property, Plant and Equipment
Property and equipment, gross	1,019	950
Furniture and fixtures
Property, Plant and Equipment
Property and equipment, gross	594	517
Leasehold improvements
Property, Plant and Equipment
Property and equipment, gross	2,124	2,100
Assets under construction
Property, Plant and Equipment
Property and equipment, gross	$ 2,456	$ 0

Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017
Payables and Accruals [Abstract]
Compensation and benefits	$ 2,500		$ 1,662
Research and development costs	6,659		339
UCLB milestone	653	$ 500	0
Professional fees	3,099		300
Deferred rent	569		197
Other liabilities	623		589
Total accrued expenses and other liabilities	14,103		3,087
Current portion of long term debt and leases	400		$ 400
Increase in accrued research and development cost	6,300
Increase in accrued professional service fees	$ 2,800

Shareholders’ Equity - Ordinary Shares (Details) - Ordinary shares	Sep. 30, 2018 $ / shares shares	Jun. 22, 2018 £ / shares	Jun. 22, 2018 $ / shares	Sep. 30, 2017 $ / shares shares
Class of Stock
Common stock, shares authorized (shares)	200,000,000			37,426,509
Common stock, par value (usd per share) \| (per share)	$ 0.000042	£ 0.000032	$ 0.000042	$ 0.000042

Shareholders’ Equity - Initial Public Offering and Impact of Corporate Reorganization (Details)			12 Months Ended
	Jun. 26, 2018 USD ($) $ / shares shares	Jun. 22, 2018 USD ($) shares	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($) shares	Jun. 22, 2018 GBP (£) shares
Class of Stock
Proceeds of issuance of ordinary shares, net of issuance costs			$ 156,920,000	$ 127,686,000	$ 32,222,000
Payment of stock issuance cost	$ 16,000,000
Equity conversion ratio		3.185
Shares outstanding (shares) \| shares			129,074,156	29,962,741	13,921,543
Ordinary shares
Class of Stock
Shares outstanding (shares) \| shares			40,146,182
Shares value			$ 2,000	$ 1,000
Ordinary shares \| IPO
Class of Stock
Number of shares issued in transaction (shares) \| shares	10,147,059
Per share price of issuance (usd per share) \| $ / shares	$ 17.00
Proceeds of issuance of ordinary shares, net of issuance costs	$ 156,500,000
Deferred Shares
Class of Stock
Shares outstanding (shares) \| shares		34,425	34,425			34,425
Shares value		$ 1.00	$ 0	0
Deferred B shares
Class of Stock
Shares outstanding (shares) \| shares		88,893,548	88,893,548			88,893,548
Shares value		$ 118,000	$ 118,000	0
Share capital registration threshold \| £						£ 50,000
Deferred C shares
Class of Stock
Shares outstanding (shares) \| shares			1
Shares value		$ 1.00	$ 0	$ 0

Shareholders’ Equity (Details) - shares	Sep. 30, 2018	Jun. 22, 2018	Sep. 30, 2017	Sep. 30, 2016
Class of Stock
Total ordinary and Deferred shares (shares)	129,074,156		29,962,741	13,921,543
Series A preferred shares
Class of Stock
Total ordinary and Deferred shares (shares)	0		24,490,705	8,994,351
Class B ordinary shares
Class of Stock
Total ordinary and Deferred shares (shares)	0		3,375,196	3,375,196
Class C ordinary shares
Class of Stock
Total ordinary and Deferred shares (shares)	0		2,096,840	1,551,996
Ordinary shares
Class of Stock
Total ordinary and Deferred shares (shares)	40,146,182
Deferred Shares
Class of Stock
Total ordinary and Deferred shares (shares)	34,425	34,425
Deferred B shares
Class of Stock
Total ordinary and Deferred shares (shares)	88,893,548	88,893,548
Deferred C Shares
Class of Stock
Total ordinary and Deferred shares (shares)	1

Share Based Compensation - 2018 Equity Incentive Plan (Narratives) (Details) - shares	12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018
Stock options
Share-based Compensation Arrangement by Share-based Payment Award
Share based compensation term (years)	10 years
Vesting Group One
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)	4 years
Award vesting percentage	25.00%
Vesting Group One \| Performance Based
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)	4 years
Award vesting percentage	25.00%
Vesting Group Two
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)	3 years
Vesting Group Two \| Performance Based
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)	3 years
2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award
Shares authorized for distribution (shares)	14,000,000
Increase in reserved shares term	10 years
Periodical increase in authorized shares (percentage)		4.00%
2018 Equity Incentive Plan \| Ordinary shares
Share-based Compensation Arrangement by Share-based Payment Award
Shares authorized for distribution (shares)		3,281,622
2018 Equity Incentive Plan - New \| Ordinary shares
Share-based Compensation Arrangement by Share-based Payment Award
Shares authorized for distribution (shares)		3,025,548
2018 Equity Incentive Plan - Shares Available Under 2017 Plan \| Ordinary shares
Share-based Compensation Arrangement by Share-based Payment Award
Shares authorized for distribution (shares)		256,074

Share Based Compensation - Options Valuation Assumptions (Details) - Stock options	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Expected term (in years)	6 years	6 years
Risk-free interest rate minimum (percentage)	2.61%	1.91%
Risk-free interest rate maximum (percentage)	3.00%	2.05%
Expected volatility minimum (percentage)	68.15%	68.61%
Expected volatility maximum (percentage)	72.99%	68.93%
Expected dividend yield (percentage)	0.00%	0.00%

Share Based Compensation - Share Options Rollforward (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding
Beginning balance (shares)	570,309	0
Granted (shares)	1,513,218	570,537
Exercised (shares)	0	0
Canceled or forfeited (shares)	(18,046)	(228)
Ending balance (shares)	2,065,481	570,309
Shares Exercisable (shares)		166,262
Vested and expected to vest (shares)		2,065,481
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price
Beginning balance (weighted average exercise price)	$ 0.51	$ 0.00
Granted (weighted average exercise price)	13.33	0.51
Exercised (weighted average exercise price)	0.00	0.00
Canceled or forfeited (weighted average exercise price)	4.99	0.00
Ending balance (weighted average exercise price)	$ 9.87	0.51
Exercisable (weighted average exercise price)		0.52
Vested or expected to vest (weighted average exercise price)		$ 9.87
Options outstanding (weighted- average remaining contractual term years)	9 years 4 months 6 days	9 years 8 months 23 days
Options exercisable (weighted- average remaining contractual term years)		8 years 8 months 23 days
Vested and expected to vest (weighted- average remaining contractual term years)		9 years 4 months 6 days
Options outstanding (aggregate intrinsic value)	$ 43,146	$ 2,024
Options exercisable (aggregate intrinsic value)		5,022
Options vested and expected to vest (aggregate intrinsic value)		$ 43,146

Share Based Compensation - Share Options (Narratives) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Granted (shares)	1,513,218	570,537
Forfeited (shares)	18,046	228
Share based compensation expense	$ 6,765	$ 3,153	$ 2,257
Non-employee compensation expense	$ 100
Stock options
Share-based Compensation Arrangement by Share-based Payment Award
Weighted average grant date fair value (usd per share)	$ 8.55	$ 4.04
Granted (shares)			0
Stock options - performance based
Share-based Compensation Arrangement by Share-based Payment Award
Granted (shares)	0	556,966
Forfeited (shares)		228
Share based compensation expense	$ 1,000	$ 400
Unrecognized stock based compensation	$ 600

Share Based Compensation - Restricted Ordinary Shares Valuation Assumptions (Details) - Restricted Ordinary Shares	May 31, 2018	Mar. 31, 2018	Sep. 25, 2017	Apr. 26, 2017	Mar. 02, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Expected term (in years)	1 year 9 months 18 days	1 year 9 months 18 days	9 months 18 days	1 year 2 months 12 days	2 years 9 months 18 days
Risk-free interest rate (percentage)	2.10%	2.10%	1.30%	1.00%	1.00%
Expected volatility (percentage)	71.00%	71.00%	71.00%	76.60%	73.20%
Expected dividend yield (percentage)	0.00%	0.00%	0.00%	0.00%	0.00%

Share Based Compensation - Restricted Ordinary Shares Rollforward (Details) - Restricted Ordinary Shares - $ / shares	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Unvested and outstanding beginning balance (shares)	1,358,317	1,266,619	416,887
Granted (shares)	0	642,150	1,070,797
Vested (shares)	(534,906)	(453,134)	(220,940)
Canceled or forfeited (shares)	(7,779)	(97,318)	(125)
Unvested and outstanding ending balance (shares)	815,632	1,358,317	1,266,619
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value
Unvested and outstanding beginning balance (weighted average grant date fair value)	$ 4.20	$ 3.89	$ 3.54
Granted (weighted average grant date fair value)	0.00	4.36	4.08
Vested (weighted average grant date fair value)	3.96	3.92	3.38
Canceled or forfeited (weighted average grant date fair value)	3.68	4.20	3.03
Unvested and outstanding ending balance (weighted average grant date fair value)	$ 4.17	$ 4.20	$ 3.89

Share Based Compensation - Restricted Ordinary Shares (Narratives) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Share based compensation expense	$ 6,765	$ 3,153	$ 2,257
Non-employee compensation expense	$ 100
Restricted Ordinary Shares
Share-based Compensation Arrangement by Share-based Payment Award
Granted (shares)	0	642,150	1,070,797
Vested (shares)	534,906	453,134	220,940
Unrecognized stock based compensation	$ 800
Non-employee compensation expense	$ 1,000	$ 200
Restricted Ordinary Shares \| Service Based
Share-based Compensation Arrangement by Share-based Payment Award
Granted (shares)		439
Restricted Ordinary Shares \| Service and Performance Based
Share-based Compensation Arrangement by Share-based Payment Award
Granted (shares)		641,711
Restricted Ordinary Shares \| Performance Based
Share-based Compensation Arrangement by Share-based Payment Award
Vested (shares)	159,492	24,896
Share based compensation expense	$ 1,000	$ 800

Share Based Compensation - Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award
Total share-based compensation	$ 6,765	$ 3,153	$ 2,257
Unrecognized stock based compensation	$ 12,200
Period for recognition of share based compensation (years)	3 years 6 months
Research and development
Share-based Compensation Arrangement by Share-based Payment Award
Total share-based compensation	$ 3,116	1,145	916
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award
Total share-based compensation	$ 3,649	$ 2,008	$ 1,341

License Agreements (Details) £ in Thousands, $ in Thousands	1 Months Ended
License Agreements (Details) £ in Thousands, $ in Thousands	Mar. 31, 2016 GBP (£) shares	Sep. 30, 2014 USD ($) shares	Sep. 30, 2018 USD ($)	Sep. 30, 2018 GBP (£)	Mar. 31, 2018 USD ($)	Sep. 30, 2017 USD ($)
Schedule Of License Agreements [Line Items]
Accrued license fees payable \| $			$ 653		$ 500	$ 0
UCLB
Schedule Of License Agreements [Line Items]
Shares issued (shares) \| shares	313,971	1,497,643
Payment of upfront fees	£ 1,500	$ 300
Annual license fee payments				£ 30
UCLB \| Regulatory Approval
Schedule Of License Agreements [Line Items]
Conditional payment, regulatory approval				35,500
UCLB \| Net Sales Levels
Schedule Of License Agreements [Line Items]
Conditional payment, regulatory approval				51,000
UCLB \| Product Sales
Schedule Of License Agreements [Line Items]
Conditional payment, regulatory approval				18,000
UCLB \| Product Sales \| Minimum
Schedule Of License Agreements [Line Items]
Conditional payment, regulatory approval				1,000
UCLB \| Product Sales \| Maximum
Schedule Of License Agreements [Line Items]
Conditional payment, regulatory approval				£ 18,500

Income Taxes - (Narratives) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income tax benefit	$ 7,280	$ 3,653	$ 1,777
Effective rate of income tax (percentage)	14.00%	15.60%	12.40%
Increase in deferred tax assets		$ 13,500
Operating loss carryforward, foreign		38,000
Deferred tax asset valuation allowances	$ 18,533	$ 4,987

Income Taxes - Reconciliation of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Net loss before taxes	$ (52,031)	$ (23,380)	$ (14,327)
U.K. statutory tax rate (percentage)	19.00%	19.50%	20.00%
Income tax benefit at U.K. statutory tax rate	$ (9,886)	$ (4,559)	$ (2,865)
Tax incentives / credits	(7,296)	(3,702)	(1,837)
Non-deductible expenses	1,553	609	694
Non-deductible expenses	(13)	13	57
Operating losses	7,317	3,754	2,168
Tax on property, plant, equipment and intangibles	233	113	0
Other, net	812	119	6
Total income tax benefit	$ (7,280)	$ (3,653)	$ (1,777)
Effective rate of income tax (percentage)	14.00%	15.60%	12.40%

Income Taxes - Deferred Tax Assets Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Deferred tax assets:
Other differences	$ 1,785	$ 11
Tax losses	6,515	3,878
Fixed assets	10,233	1,098
Total deferred tax assets	18,533	4,987
Valuation allowances	(18,533)	(4,987)
Net deferred tax asset (liability)	$ 0	$ 0

Commitments and Contingencies - (Narratives) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Loss Contingencies
Rent free period (in months)	8 months
Rent expense	$ 0.9	$ 0.6
Whitewood Media Village GP Limited and Whitewood Media Village Nominee Limited
Loss Contingencies
Lease term (in years)	8 years
Leasehold improvements	$ 2.5
The Mutual Insurance Society Limited
Loss Contingencies
Lease term (in years)	15 years
Operating lease
Loss Contingencies
Leasehold improvements	$ 0.1	2.1
Operating lease \| Imperial (Forest House) Limited
Loss Contingencies
Lease term (in years)	10 years
Period to exercise option for additional space (in months)	15 months
Licensing agreements
Loss Contingencies
Loss Contingency Accrual	$ 0.7	$ 0.0

Commitments and Contingencies - Future Minimum Lease Payment (Details) $ in Thousands	Sep. 30, 2018 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity
2019	$ 1,316
2020	1,382
2021	1,017
2022	1,070
2023	1,037
Thereafter	1,300
Total	$ 7,122

Related Party Transactions (Details)	12 Months Ended
Related Party Transactions (Details)	Sep. 30, 2018 USD ($)	Sep. 30, 2018 GBP (£)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2018 GBP (£)
Related Party Transaction
Professional fees	$ 1,000,000		$ 500,000
Affiliated Entity \| Syncona LLP
Related Party Transaction
Related party expense	60,000		56,000	$ 200,000
Due to related party	13,000		3,000
Affiliated Entity \| University College London and Related Entities
Related Party Transaction
Due to related party			200,000	43,000
Related party transactions			700,000	2,400,000
Affiliated Entity \| University College London and Related Entities \| License fees
Related Party Transaction
Related party transactions			40,000	1,500,000
Affiliated Entity \| The Wellcome Trust
Related Party Transaction
Due to related party			0	0
Affiliated Entity \| Arix Bioscience
Related Party Transaction
Related party expense	18,000		20,000	$ 11,000
Due to related party	0		2,000
Affiliated Entity \| Kapil Dhingra, M.D.
Related Party Transaction
Due to related party	$ 46,000		$ 32,000
Professional fees \| £		£ 10,000
Incremental rate for professional fees \| £					£ 1,111

Employee Benefit Plans (Details) - USD ($)	12 Months Ended
Employee Benefit Plans (Details) - USD ($)	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Retirement Benefits [Abstract]
Employer contributions to defined benefit pension schemes	$ 500,000	$ 300,000	$ 100,000
Employer contribution (percent)	4.00%
Employer contributions	$ 0	$ 0	$ 0

Subsequent Events	12 Months Ended
Subsequent Events	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company evaluated subsequent events through November 20, 2018, the date on which these financial statements were issued.

Summary of Significant Accounting Policies - Segment Information (Details)	12 Months Ended
	Sep. 30, 2018 segment region
Accounting Policies [Abstract]
Number of reportable segments \| segment	1
Number of geographic regions \| region	2

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Sep. 30, 2018
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans In the United Kingdom, the Company makes contributions to private defined benefit pension schemes on behalf of its employees. The Company paid $0.5 million, $0.3 million and $0.1 million in contributions in the years ended September 30, 2018, 2017 and 2016, respectively. In the United States, the Company established a defined contribution savings plan under Section 401(k) of the Internal Revenue Code subsequent to September 30, 2018. The plan covers substantially all U.S. employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. The Company matches employee contributions up to four percent of the employee’s annual salary. No matching contributions were recorded for the years ended September 30, 2018, 2017 and 2016. The Company pays all administrative fees related to the Plan.