Autolus Therapeutics (AUTL) 20-F 3 Mar 20 2019 FY Annual report (foreign) Financial data

Document Entity Information Sta

Document Entity Information Statement	12 Months Ended
	Dec. 31, 2019shares
Document Information [Abstract]
Entity Registrant Name	Autolus Therapeutics plc
Entity Central Index Key	0001730463
Document Type	20-F
Document Period End Date	Dec. 31, 2019
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	44,983,006
Document Annual Report	true
Document Shell Company Report	false
Document Transition Report	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash	$ 210,643,000	$ 217,450,000
Restricted cash	787,000	105,000
Prepaid expenses and other current assets	37,826,000	15,411,000
Total current assets	249,256,000	232,966,000
Non-current assets:
Property and equipment, net	28,164,000	19,968,000
Operating lease assets	23,409,000
Long-term deposits	2,040,000	1,276,000
Deferred tax asset	410,000
Intangible assets, net	254,000	0
Total assets	303,533,000	254,210,000
Current liabilities:
Accounts payable	1,075,000	2,022,000
Accrued expenses and other liabilities	21,398,000	19,054,000
Lease liability	2,511,000
Total current liabilities	24,984,000	21,076,000
Non-current liabilities:
Lease liability	23,710,000
Long-term lease incentive obligation	0	207,000
Other long-term payables	0	285,000
Total liabilities	48,694,000	21,568,000
Shareholders' equity:
Additional paid-in capital	500,560,000	361,311,000
Accumulated other comprehensive loss	(8,691,000)	(15,488,000)
Accumulated deficit	(237,150,000)	(113,301,000)
Total shareholders' equity	254,839,000	232,642,000
Total liabilities and shareholders' equity	303,533,000	254,210,000
Ordinary shares
Shareholders' equity:
Shares value	2,000	2,000
Deferred Shares
Shareholders' equity:
Shares value	0	0
Deferred B shares
Shareholders' equity:
Shares value	118,000	118,000
Deferred C shares
Shareholders' equity:
Shares value	$ 0	$ 0

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals)	Dec. 31, 2019£ / sharesshares	Dec. 31, 2019$ / sharesshares	Dec. 31, 2018£ / sharesshares	Dec. 31, 2018$ / sharesshares
Ordinary shares
Shareholders' equity:
Common stock, par value (usd/gbp per share) | $ / shares		$ 0.000042		$ 0.000042
Common stock, shares authorized (shares)	200,000,000	200,000,000	200,000,000	200,000,000
Common stock, shares, issued (shares)	44,983,006	44,983,006	40,145,617	40,145,617
Common stock, shares outstanding (shares)	44,983,006	44,983,006	40,145,617	40,145,617
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	£ 0.000008		£ 0.000008
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 Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Grant income	$ 296,000	$ 2,908,000	$ 1,407,000	$ 1,693,000
Operating expenses:
Research and development	(17,713,000)	(105,418,000)	(36,150,000)	(16,012,000)
General and administrative	(7,593,000)	(39,452,000)	(22,790,000)	(9,099,000)
Loss on impairment of leasehold improvements	0	(4,102,000)	0	0
Total operating expenses, net	(25,010,000)	(146,064,000)	(57,533,000)	(23,418,000)
Other income (expense):
Interest income	660,000	2,542,000	1,532,000	84,000
Other income (expense)	1,097,000	4,514,000	3,970,000	(46,000)
Total other income, net	1,757,000	7,056,000	5,502,000	38,000
Net loss before income tax	(23,253,000)	(139,008,000)	(52,031,000)	(23,380,000)
Income tax benefit	2,605,000	15,159,000	7,280,000	3,653,000
Net loss attributable to ordinary shareholders	(20,648,000)	(123,849,000)	(44,751,000)	(19,727,000)
Other comprehensive (loss) income:
Foreign currency exchange translation adjustment	(5,568,000)	6,797,000	(6,071,000)	802,000
Total comprehensive loss	$ (26,216,000)	$ (117,052,000)	$ (50,822,000)	$ (18,925,000)
Basic and diluted net loss per ordinary share (usd per share)	$ (0.52)	$ (2.88)	$ (1.42)	$ (1.43)
Weighted-average basic and diluted ordinary shares (shares)	39,366,634	43,065,542	31,557,034	13,783,222

Consolidated Statements of Shar

Consolidated Statements of Shareholders’ Equity Statement - USD ($) $ in Thousands	Total	Ordinary shares	Deferred Shares	Deferred B shares	Deferred C Shares	Common sharesOrdinary shares	Common sharesDeferred Shares	Common sharesDeferred B shares	Common sharesDeferred C Shares	Additional Paid in Capital	Accumulated other comprehensive loss	Accumulated deficit
Beginning balance at Sep. 30, 2016	$ 30,687					$ 0	$ 0	$ 0	$ 0	$ 63,513	$ (4,651)	$ (28,175)
Beginning balance (shares) at Sep. 30, 2016						13,921,544	0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized loss on foreign currency translation	802
Net loss	(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 of shares, net of issuance costs	$ 156,803					$ 1		$ 118		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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares, net of issuance costs	$ 3,393									3,393
Restricted shares - forfeited (shares)						(565)
Unrealized loss on foreign currency translation	(5,568)										(5,568)
Net loss	(20,648)											(20,648)
Ending, balance at Dec. 31, 2018	$ 232,642					$ 2	$ 0	$ 118	$ 0	361,311	(15,488)	(113,301)
Ending balance (shares) at Dec. 31, 2018	129,073,591	40,145,617	34,425	88,893,548	1	40,145,617	34,425	88,893,548	1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of shares, net of issuance costs	$ 108,815									108,815
Issuance, net of issuance cost (shares)						4,830,000
Share-based compensation expense	30,386									30,386
Restricted shares - forfeited (shares)						(4,335)
Exercise of stock options	$ 48									48
Exercise of stock options (shares)	11,724					11,724
Unrealized loss on foreign currency translation	$ 6,797
Net loss	(123,849)											(123,849)
Ending, balance at Dec. 31, 2019	$ 254,839					$ 2	$ 0	$ 118	$ 0	$ 500,560	$ (8,691)	$ (237,150)
Ending balance (shares) at Dec. 31, 2019	133,910,980	44,983,006	34,425	88,893,548	1	44,983,006	34,425	88,893,548	1

Consolidated Statement of Cash

Consolidated Statement of Cash Flows - USD ($)	3 Months Ended	12 Months Ended			15 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (20,648,000)	$ (123,849,000)	$ (44,751,000)	$ (19,727,000)	$ (19,727,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	645,000	4,611,000	1,709,000	1,009,000
Loss on disposal of fixed assets and intangible assets	394,000	43,000	8,000	0
Non-cash share-based compensation (net of amount capitalized)	3,393,000	30,212,000	6,765,000	3,153,000
Loss on impairment of leasehold improvements	0	4,102,000	0	0
Deferred income tax	0	(399,000)	0	0
Changes in operating assets and liabilities
Prepaid expenses and other current assets	(3,521,000)	(21,008,000)	(7,132,000)	(2,317,000)
Long-term deposits	(1,285,000)	(702,000)	0	0
Right of use asset, net		2,551,000
Accounts payable	(723,000)	(1,451,000)	838,000	434,000
Accrued expenses and other liabilities	1,960,000	4,958,000	11,026,000	1,088,000
Lease liabilities		(552,000)
Net cash used in operating activities	(19,785,000)	(101,484,000)	(31,537,000)	(16,360,000)
Cash flows from investing activities:
Purchases of property and equipment	(4,422,000)	(18,341,000)	(9,119,000)	(2,876,000)
Purchase of intangible assets	0	(327,000)	(412,000)	0
Net cash used in investing activities	(4,422,000)	(18,668,000)	(9,531,000)	(2,876,000)
Cash flows from financing activities:
Proceeds of issuance of ordinary shares, net of issuance costs	0	108,863,000	156,920,000	127,686,000
Net cash provided by financing activities	0	108,863,000	156,920,000	127,686,000
Effect of exchange rate changes on cash	(5,327,000)	5,164,000	(5,833,000)	561,000
Net increase in cash	(29,534,000)	(6,125,000)	110,019,000	109,011,000
Cash and restricted cash, beginning of period	247,089,000	217,555,000	137,070,000	28,059,000	28,059,000
Cash and restricted cash, end of period	217,555,000	211,430,000	247,089,000	137,070,000
Supplemental non-cash flow information
Cash paid for taxes	0	1,535,000	0	0
Property and equipment purchases included in accounts payable or accrued	3,343,000	2,818,000	328,000	0
Reduction in right of use asset		1,919,000
Capitalized share-based compensation	0	174,000	0	0
Reconciliation of cash and restricted cash reported within the consolidated balance sheets
Cash						$ 210,643,000	$ 217,450,000	$ 246,984,000	$ 137,070,000
Short-term restricted cash						787,000	105,000	105,000	0
Total cash and restricted cash	$ 217,555,000	$ 211,430,000	$ 247,089,000	$ 137,070,000	$ 28,059,000	$ 211,430,000	$ 217,555,000	$ 247,089,000	$ 137,070,000

Nature of the Business

Nature of the Business	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business	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 22, 2018, 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 $156.5 million , after deducting underwriting discounts and commissions and offering expenses paid by the Company. On April 15, 2019, the Company completed an underwritten public offering of 4,830,000 ADSs representing 4,830,000 ordinary shares, at a public offering price of $24.00 per ADS, which includes an additional 630,000 ADSs issued upon the exercise in full of the underwriters’ option to purchase additional ADSs. Aggregate net proceeds to the Company, after underwriting discounts and offering expenses, were $108.8 million . On January 27, 2020, the Company completed an underwritten public offering of 7,250,000 ADSs representing 7,250,000 ordinary shares, at a public offering price of $11.00 per ADS. Aggregate net proceeds to the Company, after underwriting discounts, were $75.0 million . Autolus Therapeutics plc is a continuation of Autolus Limited and its subsidiaries. In connection with the IPO, the Company completed a corporate reorganization, which 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 $123.8 million for the year ended December 31, 2019 , $20.6 million for the three months ended December 31, 2018, and $44.8 million and $19.7 million for the years ended September 30, 2018 and 2017, respectively. In addition, as of December 31, 2019 and 2018 , the Company had an accumulated deficit of $237.2 million and $113.3 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 December 31, 2019 of $210.6 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 Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	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, 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 cash and cash equivalents in the consolidated financial statements to include cash at banks with a maturity of less than three months, which is subject to an insignificant risk of changes in value. Restricted Cash The Company entered into a lease that requires a letter of credit supported by $0.6 million deposit held by the Company's bank for the duration of the lease and a credit card arrangement that requires a security deposit of $0.2 million . The Company includes the restricted cash balance in cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts shown on the Company's consolidated statements of cash flows. 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 December 31, 2019 and 2018 , 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 , lab equipment has an estimated useful life of five or ten years , 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 recognized a loss on impairment of $4.1 million for the year ended December 31, 2019 related to leasehold improvements as the Company chose to discontinue the fit-out of the Company's manufacturing capacity at the Enfield, U.K. facility, no impairments or disposals for the three months ended December 31, 2018, an asset disposal of less than $10,000 for the year ended September 30, 2018 , and did not recognize any impairment losses from its inception through September 30, 2017 . The Company routinely evaluates the useful life attributed to its assets. During the second quarter ended June 30, 2019, the Company determined that the useful lives of certain lab equipment should be increased from five -years to ten -years based on expectation of future usability. The Company accounted for this as a change in estimate that was applied prospectively, effective April 1, 2019. This change in useful life resulted in a reduction of depreciation expense of $0.3 million , and an increase in basic and diluted earnings per share of $0.01 , for the year ended December 31, 2019. Leases Effective January 1, 2019, the Company adopted Accounting Standards Codification (“ASC”), Topic 842, Leases (“ASC 842”), using the required modified retrospective approach and utilizing the effective date as its date of initial application, for which prior periods are presented in accordance with the previous guidance in ASC 840, Leases. At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present. Most leases with a term greater than one year are recognized on the balance sheet as right-of-use assets, lease liabilities and, if applicable, long-term lease liabilities. The Company has elected not to recognize on the balance sheet leases with terms of one year or less. Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected remaining lease term. However, certain adjustments to the right-of-use asset may be required for items such as incentives received, initial direct costs, or prepayments. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rates, which are the rates incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. In accordance with the guidance in ASC 842, components of a lease should be split into three categories: lease components (e.g. land, building, etc.), non-lease components (e.g. common area maintenance, consumables, etc.), and non-components (e.g. property taxes, insurance, etc.). Then the fixed and in-substance fixed contract consideration (including any related to non-components) must be allocated based on the respective relative fair values to the lease components and non-lease components. Although separation of lease and non-lease components is required, certain practical expedients are available. Entities may elect the practical expedient to not separate lease and non-lease components. Rather, they would account for each lease component and the related non-lease component together as a single component. For new and amended leases beginning in 2019, the Company has elected this practical expedient to account for the lease and non-lease components for leases for classes of all underlying assets and allocate all of the contract consideration to the lease component only. The Company determined the underlying lease to be the predominant component, and therefore, the entire agreement will be accounted for under ASC 842. Intangible Assets Subject to Amortization The Company’s intangible assets have been related to acquired software licenses 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 did no t recognize an impairment loss in the year ended December 31, 2019. The Company recognized an impairment loss of $0.4 million for the three months ended December 31, 2018 related to software the Company elected to discontinue. The Company did no t recognize an impairment loss in the years ended September 30, 2018 and 2017. 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. 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 Prior to the adoption of ASC 842, rent expense and lease incentives from operating leases were 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. Upon adoption of ASC 842, the Company no longer records or presents deferred rent. 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 for the year end December 31, 2019, $37,000 for the three months ended December 31, 2018, and $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 Clinical Research Organizations 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. The Company accounts for forfeitures as they occur. 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. The measurement date for employee awards is the date of grant, and share-based compensation costs are recognized as expense over the employees’ requisite service period, which is the vesting period, on an accelerated basis. The Company has adopted Accounting Standards Update (“ASU”) No. 2018-07, “Compensation —Stock Compensation (Topic 718): Improvements to Non-employee Share-Based Payment Accounting” (“ASU No. 2018-07”), as discussed below under “Recently Adopted Accounting Pronouncements,” prior to which the measurement date for non-employee awards was generally the date the services were completed, resulting in financial reporting period adjustments to share-based compensation during the vesting terms for changes in the fair value of the awards. After the adoption of ASU No. 2018-07, the measurement date for non-employee awards is the later of the adoption date of ASU No. 2018-07 or the date of grant, without changes in the fair value of the award. 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 consolidated 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. When considering the fair value of options granted in the period prior to the IPO, the Company 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 its equity value implied by the purchase price of the series A preference shares in September 2017. In March and May 2018, the Company 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 $4.6 million for the year ended December 31, 2019 , $1.1 million foreign exchange gain for the three months ended December 31, 2018, and a $4.0 million foreign exchange gain 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 $2.0 million for the year ended December 31, 2019 , $0.2 million for the three months ended December 31, 2018, and $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 gain or 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 gain of $6.8 million for the year ended December 31, 2019 , a loss of $5.6 million for the three months ended December 31, 2018, a loss $6.1 million for the year ended September 30, 2018 and a gain of $0.8 million for the years ended September 30, 2017, respectively to foreign currency translation. 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 December 31, Three Months Ended December 31, Years Ended September 30, 2019 2018 2018 2017 Unvested restricted shares and units 814,744 708,834 815,632 1,358,317 Incentive share options 5,963,239 3,711,274 2,065,481 570,309 Total 6,777,983 4,420,108 2,881,113 1,928,626 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 adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”), which requires a lessee to recognize assets and liabilities on the balance sheet for most leases and changes many key definitions, including the definition of a lease. The new standard includes a short-term lease exception for leases with a term of 12 months or less, as part of which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases using classification criteria that are substantially similar to the previous guidance. ASU 2016-02 became effective beginning January 1, 2019 requiring the use of a modified retrospective transition approach applied at the beginning of the earliest comparative period presented in the financial statements. In July 2018, the FASB issued ASU 2018-11, Leases, Targeted Improvements, (“ASU 2018-11”), which contains certain amendments to ASU 2016-02 intended to provide relief in implementing the new standard. ASU 2018-11 provides registrants with an option to not restate comparative periods presented in the financial statements. The Company elected this new transition approach using a cumulative-effect adjustment on the effective date of the standard, for which comparative periods are to be presented in accordance with the previous guidance in ASC 840, Leases. In adopting the new standard the Company elected to utilize the available package of practical expedients permitted under the transition guidance within t

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following (in thousands): December 31, 2019 2018 Research and development claims receivable $ 27,567 $ 10,272 Prepayments 7,023 2,069 VAT receivable 1,928 1,973 Other asset 279 — Grant income receivable 547 661 Other receivable 482 436 Total prepaid expenses and other current assets $ 37,826 $ 15,411 The increase to research and development claims receivable is the result of the increased income tax benefit from increased research and development expenses.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): December 31, 2019 2018 Lab equipment $ 18,214 $ 10,771 Office equipment 2,211 1,610 Furniture and fixtures 1,301 599 Leasehold improvements 10,316 2,076 Assets under construction 4,687 8,620 Less: accumulated depreciation (8,565 ) (3,708 ) Total property and equipment, net $ 28,164 $ 19,968 Depreciation expense recorded for the year ended December 31, 2019 was $4.6 million , the three months ended December 31, 2018 was $0.6 million and, for the years ended September 30, 2018 and 2017 were $1.7 million and $1.0 million , respectively. The increase in leasehold improvements is related to the build out of the Company's Media Works facility.

Intangible Asset

Intangible Asset	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Asset	Intangible Asset The following table summarizes the carrying amount of the Company's intangible assets, net of accumulated amortization: December 31, 2019 Estimated Life Cost Accumulated Amortization Net Software license 3 $ 336 $ (82 ) $ 254 Amortization expense for the year ended December 31, 2019 was $47,000 . Assuming no changes in the gross cost basis of intangible assets, the total estimated amortization expense for finite-lived intangible assets is approximately $104,000 , $88,000 , and $62,000 for each of the years ending December 31, 2020 through December 31, 2022.

Accrued Expenses and Other Liab

Accrued Expenses and Other Liabilities	12 Months Ended
	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued Expenses and Other Liabilities	Accrued Expenses and Other Liabilities Accrued expenses and other liabilities consisted of the following (in thousands): December 31, 2019 2018 Compensation and benefits $ 6,568 $ 3,296 Research and development costs 10,449 9,362 UCLB milestone 663 638 Professional fees 2,611 4,130 Deferred rent 0 561 Corporate tax 391 620 Other liabilities 716 447 Total accrued expenses and other liabilities $ 21,398 $ 19,054 Other liabilities primarily consist of the current portion lease incentive liability, together amounts of $0.3 million and $0.4 million are recorded as of December 31, 2019 and 2018 , respectively.

Shareholders_ Equity

Shareholders’ Equity	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Shareholders’ Equity	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 December 31, 2019 , the Company has not declared any dividends. Effective from June 26, 2018, the board of directors has the authority to allot new ordinary shares or to grant rights to subscribe for or to convert any security into ordinary shares in the Company up to a maximum aggregate nominal amount of $8,400 . This authority runs for five years and will expire on June 26, 2023. Effective from June 26, 2018, the board also has the authority to allot ordinary shares for cash or to grant rights to subscribe for or to convert any security into ordinary shares in the Company without first offering them to existing shareholders in proportion to their existing holdings up to an aggregate maximum nominal amount of $0 . This authority runs for five years and will expire on June 26, 2023. As of December 31, 2019, the Company’s issued capital share consisted of 44,983,006 ordinary shares, with a nominal value of $0.000042 per share, (ii) 34,425 deferred shares, with a nominal value of £0.00001 per share, (iii) 88,893,548 B deferred shares, with a nominal value of £0.00099 per share and (iv) 1 C deferred share, with a nominal value of £0.000008 . Each issued share has been fully paid. 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 the Company 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 shares in the consolidated Balance sheets reflect the number of ordinary shares and deferred shares authorized, issued, and outstanding at December 31, 2019 and 2018 , and also reflects the conversion of preferred and ordinary shares on 3.185 -for-1 basis upon completion of the Company's IPO. December 31, September 30, 2019 2018 2018 2017 Series A preferred shares — — — 24,490,705 Class B ordinary shares — — — 3,375,196 Class C ordinary shares — — — 2,096,840 Ordinary Shares 44,983,006 40,145,617 40,146,182 — Deferred shares 34,425 34,425 34,425 — Deferred B shares 88,893,548 88,893,548 88,893,548 — Deferred C share 1 1 1 — Total Ordinary and Deferred Shares 133,910,980 129,073,591 129,074,156 29,962,741

Share Based Compensation

Share Based Compensation	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Share Based Compensation	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. The updated maximum number of ordinary shares that may be issued under the 2018 Plan is 6,686,764 as of December 31, 2019. The total 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. Restricted stock units awarded in December 2019 vest over a 3 -year service period with 50% of the award vesting one-and-half years from commencement date and the remaining 50% of the award vesting at the end of the third year. 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 December 31, 2019 and 2018 were as follows: Year Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2018 2017 Expected option life (years) 5.27 to 6.08 6.08 6.08 6.08 Risk-free interest rate 1.39% to 2.66% 2.70% to 3.09% 2.61% to 3.00% 1.91% to 2.05% Expected volatility 72.30% to 76.22% 69.52% to 71.26% 68.15% to 72.99% 68.61% to 68.93% Expected dividend yield —% —% —% —% Share Options The table below summarizes activity for the year ended December 31, 2019. Number of Weighted- Weighted- Aggregate Outstanding as of December 31, 2018 3,711,274 $ 19.25 9.47 $ 51,464 Granted 2,438,145 15.22 — — Exercised (11,724 ) 3.94 — $ 198 Forfeited (201,456 ) 19.72 — — Outstanding as of December 31, 2019 5,936,239 $ 17.71 9.02 $ 11,873 Exercisable as of December 31, 2019 1,466,625 $ 16.34 8.63 $ 6,124 Vested and expected to vest as of December 31, 2019 5,936,239 $ 17.71 9.02 $ 11,873 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 was $10.07 , $20.04 , $8.55 and $4.04 per share for the year ended December 31, 2019, for the three months ended December 31, 2018, and for the years ended September 30, 2018 and 2017, respectively. As of December 31, 2019, the total unrecognized compensation expense related to unvested options was $34.0 million , which the Company expects to recognize over a weighted average vesting period of 3.4 years . 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 December 31, 2019 and 2018 are as follows and reflect the conversion of ordinary shares in the current and previous years. Number of Weighted average grant date fair value Unvested and outstanding at December 31, 2018 708,834 $ 4.10 Granted 0 0.00 Vested (389,755 ) 4.31 Forfeited (4,335 ) 4.43 Unvested and outstanding at December 31, 2019 314,744 9.05 As of December 31, 2019 , there was unrecognized compensation of $0.3 million , which will be recognized over 1.5 years . Restricted Stock Units A restricted stock unit (“RSU”) represents the right to receive one of the Company’s ADSs upon vesting of the RSU. The fair value of each RSU is based on the closing price of the Company’s ADSs on the date of grant. The Company grants RSUs with service conditions that vest over 3 -year service period with 50% of the award vesting one-and-half years from commencement date and the remaining 50% of the award vesting at the end of the third year. During the year ended December 31, 2019, the Company granted 500,000 RSUs under the 2018 Plan. The following is a summary of RSU activity for the 2018 Plan for the years ended December 31, 2019 and 2018, respectively: Number of Weighted average Unvested and outstanding at December 31, 2018 — $ — Granted 500,000 12.09 Vested — — Forfeited — — Unvested and outstanding at December 31, 2019 500,000 12.09 As of December 31, 2019, there was $5.9 million of unrecognized compensation costs related to unvested RSUs, which are expected to be recognized over a weighted average period of 3 years . Share-based Compensation Expense Share-based compensation expense recorded as research and development and general and administrative expenses is as follows (in thousands): Year Ended December 31, Three Months December 31, Years Ended September 30, 2019 2018 2018 2017 Research and development $ 17,761 $ 1,906 $ 3,116 $ 1,145 General and administrative 12,451 1,487 3,649 2,008 Capitalized to fixed assets 174 — — — Total share-based compensation $ 30,386 $ 3,393 $ 6,765 $ 3,153

License Agreements

License Agreements	12 Months Ended
	Dec. 31, 2019
License Agreements [Abstract]
License Agreements	License Agreements University College of London Business (UCLB) 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. Noile-Immune Biotech Inc. In November 2019, the Company entered into an exclusive license agreement (the “License”) with Noile-Immune Biotech Inc. ("Noile"). The Company will have the right to develop CAR T cell therapies incorporating Noile’s PRIME (proliferation-inducing and migration-enhancing) technology. The PRIME technology is designed to improve proliferation and trafficking into solid tumors of both engineered CAR T cells as well as the patient’s own T cells. The Company paid an upfront fee and may be obligated to make additional payments to Noile under the License Agreement upon the achievement of development milestones and receipt of regulatory approvals product sale milestones, as well as royalty payments based on possible future sales resulting from the utilization of the licensed technology.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company recorded an income tax benefit of $15.2 million , $2.6 million , $7.3 million and $3.7 million for the year ended December 31, 2019 , the three months ended December 31, 2018, and 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): Year ended December 31, Three months ended December 31, Year ended September 30, 2019 2018 2018 2017 Net loss before taxes $ (139,008 ) $ (23,253 ) $ (52,031 ) $ (23,380 ) U.K. statutory tax rate 19.0 % 19.0 % 19.0 % 19.5 % Income tax benefit at U.K. statutory tax rate (26,411 ) (4,423 ) (9,886 ) (4,559 ) Tax incentives / credits (16,312 ) (3,234 ) (7,296 ) (3,702 ) Non-deductible expenses 4,048 127 1,553 609 Adjustments in respect of prior years 96 265 (13 ) 13 Operating losses 21,643 3,605 7,317 3,754 Tax on property, plant, equipment and intangibles 267 140 233 113 Other, net 1,510 915 812 119 Total income tax benefit $ (15,159 ) $ (2,605 ) $ (7,280 ) $ (3,653 ) Current income tax benefit (14,749 ) (2,605 ) (7,280 ) (3,653 ) Deferred income tax benefit (410 ) — — — Effective rate of income tax 10.9 % 11.2 % 14.0 % 15.6 % The effective tax rates in the above table for the year ended December 31, 2019 , the three months ended December 31, 2018 , and the years ended September 30, 2018 and 2017 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 December 31, 2019 and 2018 (in thousands): December 31, 2019 2018 Deferred tax assets: Other differences $ 1,522 $ 2,870 Tax losses 19,624 7,851 Fixed assets 896 621 Total deferred tax assets 22,042 11,342 Valuation allowances (21,632 ) (11,342 ) Net deferred tax asset (liability) $ 410 $ — Deferred tax assets resulting from loss carry forwards, fixed assets and retirement benefits, with total deferred tax assets increasing by $10.7 million in 2019 . The Company has recorded a valuation allowance against the net deferred tax asset where the recoverability due to future taxable profits is unknown. The $0.4 million deferred tax asset balance is related to the Company's U.S. entity. At December 31, 2019 , the Company had U.K. trading losses carry forward of $115.4 million . These losses are carried forward 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 $21.6 million and $11.3 million at December 31, 2019 and 2018 , respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	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 December 31, 2019 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 December 31, 2019. As of December 31, 2019 , 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 December 31, 2019 . Leases The Company leases certain office space, laboratory space, and equipment. At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present. The Company does not recognize right-of-use assets or lease liabilities for leases determined to have a term of 12 months or less. Many of the Company's leases contain variable non-lease components such as maintenance, taxes, insurance, and similar costs for the spaces it occupies. For new and amended leases beginning in 2019, the Company has elected the practical expedient not to separate these non-lease components of leases for classes of all underlying assets and instead account for them as a single lease component for all leases. The Company recognizes on a straight-lines basis the net fixed payments of operating leases over the lease term. Variable executory costs, as it relates to net leases, are excluded from the calculation of the lease liability and the Company expenses the variable lease payments in the period in which it incurs the obligation to pay such variable amounts and will be included in variable lease costs in the leases footnote disclosure. These variable lease payments are not included in the Company's calculation of its right-of-use assets or lease liabilities. In adopting ASC 842, the Company elected the package of practical expedients which, among other things, allowed it to retain the classification of its leases in place at the effective date of ASC 842. The Company’s corporate headquarters are located in London, United Kingdom. As of December 31, 2019 and 2018 , 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 and the landlord has the option to give notice to terminate the lease from September 2020 onward. The Company has measured its right-of-use assets and lease liabilities based on lease terms ending in September 2025, as the Company is reasonably certain it will not terminate the lease prior to September 2025. In addition to base rent, the Company is obligated to pay its proportionate share of building operating expenses and real estate taxes in excess of base year amounts. These costs are considered to be variable lease payments and are not included in the determination of the lease’s right-of-use asset or lease liability. Prior to the lease commencement date of the Forest House 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. The lease related to this facility is classified as an operating lease. In September 2017, the Company executed an arrangement with Catapult Limited to lease a manufacturing suite at the Cell and Gene Therapy Catapult manufacturing center in Stevenage, United Kingdom for a term through May 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 a six -month rent-free period. In addition to base rent, the Company is obligated to pay its proportionate share of building operating expenses and real estate taxes in excess of base year amounts. These costs are considered to be variable lease payments and are not included in the determination of the lease’s right-of-use asset or lease liability. In December 2018, the Company executed an additional lease arrangement for additional manufacturing space for a term through September 2023, at which time the Company has the option to renew or terminate the lease. In June 2018, the Company signed a binding letter of intent to enter into a lease for office and laboratory space in White City, London. The letter of intent required the Company to enter into a ten -year lease provided that the landlord completed the required leasehold improvements described in the agreement. The leasehold improvements were completed and the lease commenced in January 2019. The Company has the option to terminate the lease in November 2026. In addition to base rent, the Company is obligated to pay its proportionate share of building operating expenses and real estate taxes in excess of base year amounts. These costs are considered to be variable lease payments and are not included in the determination of the lease’s right-of-use asset or lease liability. The lease agreement includes an option to lease additional space. As of December 31, 2019, the Company capitalized $8.2 million as leasehold improvements. In September 2018, the Company signed a binding letter of intent to enter into a lease for manufacturing space in Enfield, United Kingdom. The letter of intent required the Company to enter into a 15 -year lease provided that the landlord completed the required leasehold improvements described in the agreement. The Company executed lease agreements for three manufacturing space units, each for 15 -year lease terms. The leases commenced in February 2019 with option to terminate the lease in February 2029. In addition to base rent, the Company is obligated to pay its proportionate share of building operating expenses and real estate taxes in excess of base year amounts. These costs are considered to be variable lease payments and are not included in the determination of the lease’s right-of-use asset or lease liability. The Company expensed $4.1 million of leasehold improvements from assets under construction as of December 31, 2019 as a result of discontinuing the fit-out of the manufacturing facility. The Company reduced the right-of-use asset and lease liability based on the contractual option termination date. The Company is actively seeking to sub-lease or assign the lease arrangement to a third party. The Company completed an asset impairment analysis of the right-of-use lease concluding the undiscounted cash flow exceeded the carry value as of December 31, 2019. In October 2018, the Company executed an agreement to sublease office space in Rockville, Maryland for a term through October 2021. The lease related to this facility is classified as an operating lease. The lease had a four -month rent-free period. In addition to base rent, the Company is obligated to pay its proportionate share of building operating expenses and real estate taxes in excess of base year amounts. These costs are considered to be variable lease payments and are not included in the determination of the lease’s right-of-use asset or lease liability. In January 2019, the Company executed a lease agreement to lease additional office and manufacturing space in Rockville, Maryland. The lease agreement required the Company to enter into a 16 -year lease provided that the landlord completes the required leasehold improvements described in the agreement. The Company expects the lease to commence in June 2020 for a term through June 2036. The Company has capitalized $2.2 million in leasehold improvements as assets under construction as of December 31, 2019 . The Company excluded the $57.9 million of undiscounted future minimum lease payments in the maturity of lease liabilities table as the lease had not yet commenced as of December 31, 2019 . The Company identified and assessed the following significant assumptions in recognizing its right-of-use assets and corresponding lease liabilities: • As the Company's leases do not provide an implicit rate, it estimated the incremental borrowing rate for each lease based on a yield curve analysis, utilizing the interest rate derived from the fair value analysis of its existing leases and adjusting it for factors that appropriately reflect the profile of secured borrowing over the lease term. For leases existing as of the adoption date, the Company has utilized its incremental borrowing rate based on the remaining lease term as of the adoption date. For leases that commenced after the adoption date, the Company determined the incremental borrowing rate based on the lease term as determined at the commencement date of the lease. • The expected lease terms include both contractual lease periods and, when applicable, cancelable option periods where failure to exercise such options would result in an economic penalty. • Since the Company elected to account for each lease component and its associated non-lease components as a single combined lease component, all contract consideration was allocated to the combined lease component. Leases (in thousands) Balance Sheet Classification As of December 31, 2019 Assets Operating lease assets Operating right-of-use assets $ 23,409 Liabilities Current Operating lease liabilities Current liabilities: Operating lease liabilities $ 2,511 Noncurrent Operating lease liabilities Non-current liabilities: Operating lease liabilities $ 23,710 Total lease liabilities $ 26,221 Lease cost (in thousands) Statement of Operations Classification Year Ended December 31, 2019 Operating lease cost Operating expenses: research and development $ 3,156 Variable lease cost Operating expenses: research and development 1,222 Operating lease cost Operating expenses: general and administrative 1,241 Variable lease cost Operating expenses: general and administrative 250 Short term lease costs 270 Total lease cost $ 6,139 Other information (in thousands) December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 2,415 Right-of-use assets obtained in exchange for new operating lease liabilities $ 26,124 Weighted-average remaining lease term — operating leases (years) 7.7 Weighted-average discount rate — operating leases 6.8 % Future fixed payments for non-cancellable operating leases in effect as of December 31, 2019 are payable as follows: Operating Leases Maturity of lease liabilities for the years ending December 31, (in thousands) 2020 4,232 2021 5,039 2022 4,460 2023 4,359 2024 3,869 Thereafter 12,222 Total lease payments 34,181 Less: imputed interest (7,943 ) Less: foreign exchange (gain)/loss (17 ) Present value of lease liabilities 26,221 The above table excludes $57.9 million of minimum lease payments for leases signed but not yet commenced as of December 31, 2019 . The following table summarizes the future minimum lease payments due under operating leases as of December 31, 2018 prior to the adoption of ASC 842 (in thousands): Year ending December 31, 2019 $ 2,244 2020 2,332 2021 1,934 2022 1,324 2023 1,196 Thereafter 1,121 Total $ 10,151 The Company recognized 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 prior to the adoption of ASC 842. The Company recorded rent expense totaling $0.5 million for the three months ended December 31, 2018, and $0.9 million and $0.6 million for the years ended September 30, 2018 and 2017, respectively.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2019
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 expensed $1.0 million , $0.2 million , $0.5 million , and $0.3 million in contributions in the year ended December 31, 2019 , three months ended December 2018, and the years ended September 30, 2018 and 2017, 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. The Company expensed $0.2 million and $18,000 in contributions in the year ended December 31, 2019 and the three months ended December 31, 2018, respectively. No matching contributions were recorded for the years ended September 30, 2018, and 2017. The Company pays all administrative fees related to the Plan.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company evaluated subsequent events through March 3, 2020, the date on which these financial statements were issued. On January 27, 2020, the Company completed an underwritten public offering of 7,250,000 ADSs representing 7,250,000 ordinary shares, at a public offering price of $11.00 per ADS. Aggregate net proceeds to the Company, after underwriting discounts, were $75.0 million . On February 27, 2020, the Company terminated its sublease for 27,502 square feet of office space in Rockville, Maryland and concurrently entered into a direct lease with the building owner for the same premises. The lease is non-cancellable and is scheduled to terminate in March 2025.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
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, 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 cash and cash equivalents in the consolidated financial statements to include cash at banks with a maturity of less than three months, which is subject to an insignificant risk of changes in value.
Restricted Cash	Restricted Cash The Company entered into a lease that requires a letter of credit supported by $0.6 million deposit held by the Company's bank for the duration of the lease and a credit card arrangement that requires a security deposit of $0.2 million . The Company includes the restricted cash balance in cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts shown on the Company's consolidated statements of cash flows.
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 December 31, 2019 and 2018 , 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 , lab equipment has an estimated useful life of five or ten years , 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 recognized a loss on impairment of $4.1 million for the year ended December 31, 2019 related to leasehold improvements as the Company chose to discontinue the fit-out of the Company's manufacturing capacity at the Enfield, U.K. facility, no impairments or disposals for the three months ended December 31, 2018, an asset disposal of less than $10,000 for the year ended September 30, 2018 , and did not recognize any impairment losses from its inception through September 30, 2017 .
Leases, Deferred Rent and Lease Incentives	Deferred Rent and Lease Incentives Prior to the adoption of ASC 842, rent expense and lease incentives from operating leases were 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. Upon adoption of ASC 842, the Company no longer records or presents deferred rent Leases Effective January 1, 2019, the Company adopted Accounting Standards Codification (“ASC”), Topic 842, Leases (“ASC 842”), using the required modified retrospective approach and utilizing the effective date as its date of initial application, for which prior periods are presented in accordance with the previous guidance in ASC 840, Leases. At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present. Most leases with a term greater than one year are recognized on the balance sheet as right-of-use assets, lease liabilities and, if applicable, long-term lease liabilities. The Company has elected not to recognize on the balance sheet leases with terms of one year or less. Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected remaining lease term. However, certain adjustments to the right-of-use asset may be required for items such as incentives received, initial direct costs, or prepayments. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rates, which are the rates incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. In accordance with the guidance in ASC 842, components of a lease should be split into three categories: lease components (e.g. land, building, etc.), non-lease components (e.g. common area maintenance, consumables, etc.), and non-components (e.g. property taxes, insurance, etc.). Then the fixed and in-substance fixed contract consideration (including any related to non-components) must be allocated based on the respective relative fair values to the lease components and non-lease components. Although separation of lease and non-lease components is required, certain practical expedients are available. Entities may elect the practical expedient to not separate lease and non-lease components. Rather, they would account for each lease component and the related non-lease component together as a single component. For new and amended leases beginning in 2019, the Company has elected this practical expedient to account for the lease and non-lease components for leases for classes of all underlying assets and allocate all of the contract consideration to the lease component only. The Company determined the underlying lease to be the predominant component, and therefore, the entire agreement will be accounted for under ASC 842.
Intangible Assets Subject to Amortization	Intangible Assets Subject to Amortization The Company’s intangible assets have been related to acquired software licenses 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.
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. 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.
Research and Development Costs	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. 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 Clinical Research Organizations 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	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. The Company accounts for forfeitures as they occur. 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. The measurement date for employee awards is the date of grant, and share-based compensation costs are recognized as expense over the employees’ requisite service period, which is the vesting period, on an accelerated basis. The Company has adopted Accounting Standards Update (“ASU”) No. 2018-07, “Compensation —Stock Compensation (Topic 718): Improvements to Non-employee Share-Based Payment Accounting” (“ASU No. 2018-07”), as discussed below under “Recently Adopted Accounting Pronouncements,” prior to which the measurement date for non-employee awards was generally the date the services were completed, resulting in financial reporting period adjustments to share-based compensation during the vesting terms for changes in the fair value of the awards. After the adoption of ASU No. 2018-07, the measurement date for non-employee awards is the later of the adoption date of ASU No. 2018-07 or the date of grant, without changes in the fair value of the award. 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 consolidated 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 $4.6 million for the year ended December 31, 2019 , $1.1 million foreign exchange gain for the three months ended December 31, 2018, and a $4.0 million foreign exchange gain 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 and Income Tax Credit	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 gain or 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 adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”), which requires a lessee to recognize assets and liabilities on the balance sheet for most leases and changes many key definitions, including the definition of a lease. The new standard includes a short-term lease exception for leases with a term of 12 months or less, as part of which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases using classification criteria that are substantially similar to the previous guidance. ASU 2016-02 became effective beginning January 1, 2019 requiring the use of a modified retrospective transition approach applied at the beginning of the earliest comparative period presented in the financial statements. In July 2018, the FASB issued ASU 2018-11, Leases, Targeted Improvements, (“ASU 2018-11”), which contains certain amendments to ASU 2016-02 intended to provide relief in implementing the new standard. ASU 2018-11 provides registrants with an option to not restate comparative periods presented in the financial statements. The Company elected this new transition approach using a cumulative-effect adjustment on the effective date of the standard, for which comparative periods are to be presented in accordance with the previous guidance in ASC 840, Leases. In adopting the new standard the Company elected to utilize the available package of practical expedients permitted under the transition guidance within the new standard, which does not require the reassessment of the following: i) whether existing or expired arrangements are or contain a lease, ii) the lease classification of existing or expired leases, and iii) whether previous initial direct costs would qualify for capitalization under the new lease standard. Additionally, the Company made an accounting policy election to keep leases with a term of 12 months or less off of its balance sheet. Upon adoption of the standard on January 1, 2019, the Company recognized $6.3 million and $5.6 million of operating lease liabilities and right-of-use assets, respectively, on the Company’s balance sheet relating to its leases of its London, United Kingdom corporate office and manufacturing leases, and its Rockville, Maryland office lease. The adoption of the standard did not have a material effect on the Company's statements of operations or statement of cash flows. In June 2018, the FASB issued ASU 2018-07, Compensation—Stock Compensation (Topic 718) Improvements to Nonemployee Share-Based Payment Accounting (“ASU 2018-07”). These amendments expand the scope of Topic 718, Compensation—Stock Compensation (which currently only includes share-based payments to employees) to include share-based payments issued to nonemployees for goods or services. Consequently, the accounting for share-based payments to nonemployees and employees will be substantially aligned. The ASU supersedes Subtopic 505-50, Equity—Equity-Based Payments to Non-Employees. This standard is effective for public companies for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. The Company adopted this guidance effective January 1, 2019. The adoption of ASU No. 2018-07 did not have a material effect on the Company’s consolidated financial statements. Recently issued accounting pronouncements not adopted In August 2018, the FASB issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, a new standard on a customer's accounting for implementation, set-up, and other upfront costs incurred in a cloud computing arrangement (CCA) that aligns the requirements for capitalizing implementation costs in a CCA service contract with existing internal-use software guidance. The standard also provides classification guidance on these implementation costs as well as additional quantitative and qualitative disclosures. The standard is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted, and can be adopted prospectively or retrospectively. The Company adopted the new standard on January 1, 2020 on a prospective basis and are continuing to establish new processes and internal controls that may be required to comply with the new cloud computing standard.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Schedule of Antidilutive Securities	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 December 31, Three Months Ended December 31, Years Ended September 30, 2019 2018 2018 2017 Unvested restricted shares and units 814,744 708,834 815,632 1,358,317 Incentive share options 5,963,239 3,711,274 2,065,481 570,309 Total 6,777,983 4,420,108 2,881,113 1,928,626

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): December 31, 2019 2018 Research and development claims receivable $ 27,567 $ 10,272 Prepayments 7,023 2,069 VAT receivable 1,928 1,973 Other asset 279 — Grant income receivable 547 661 Other receivable 482 436 Total prepaid expenses and other current assets $ 37,826 $ 15,411

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): December 31, 2019 2018 Lab equipment $ 18,214 $ 10,771 Office equipment 2,211 1,610 Furniture and fixtures 1,301 599 Leasehold improvements 10,316 2,076 Assets under construction 4,687 8,620 Less: accumulated depreciation (8,565 ) (3,708 ) Total property and equipment, net $ 28,164 $ 19,968

Intangible Asset (Tables)

Intangible Asset (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Finite Lived intangible Asset	The following table summarizes the carrying amount of the Company's intangible assets, net of accumulated amortization: December 31, 2019 Estimated Life Cost Accumulated Amortization Net Software license 3 $ 336 $ (82 ) $ 254

Accrued Expenses and Other Li_2

Accrued Expenses and Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2019
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued expenses and other liabilities consisted of the following (in thousands): December 31, 2019 2018 Compensation and benefits $ 6,568 $ 3,296 Research and development costs 10,449 9,362 UCLB milestone 663 638 Professional fees 2,611 4,130 Deferred rent 0 561 Corporate tax 391 620 Other liabilities 716 447 Total accrued expenses and other liabilities $ 21,398 $ 19,054

Shareholders_ Equity (Tables)

Shareholders’ Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Schedule of Shares Outstanding	The shares in the consolidated Balance sheets reflect the number of ordinary shares and deferred shares authorized, issued, and outstanding at December 31, 2019 and 2018 , and also reflects the conversion of preferred and ordinary shares on 3.185 -for-1 basis upon completion of the Company's IPO. December 31, September 30, 2019 2018 2018 2017 Series A preferred shares — — — 24,490,705 Class B ordinary shares — — — 3,375,196 Class C ordinary shares — — — 2,096,840 Ordinary Shares 44,983,006 40,145,617 40,146,182 — Deferred shares 34,425 34,425 34,425 — Deferred B shares 88,893,548 88,893,548 88,893,548 — Deferred C share 1 1 1 — Total Ordinary and Deferred Shares 133,910,980 129,073,591 129,074,156 29,962,741

Share Based Compensation (Table

Share Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Schedule of Stock Options Valuation Assumptions	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 December 31, 2019 and 2018 were as follows: Year Ended December 31, Three Months Ended December 31, Year Ended September 30, 2019 2018 2018 2017 Expected option life (years) 5.27 to 6.08 6.08 6.08 6.08 Risk-free interest rate 1.39% to 2.66% 2.70% to 3.09% 2.61% to 3.00% 1.91% to 2.05% Expected volatility 72.30% to 76.22% 69.52% to 71.26% 68.15% to 72.99% 68.61% to 68.93% Expected dividend yield —% —% —% —%
Stock Option Rollforward	The table below summarizes activity for the year ended December 31, 2019. Number of Weighted- Weighted- Aggregate Outstanding as of December 31, 2018 3,711,274 $ 19.25 9.47 $ 51,464 Granted 2,438,145 15.22 — — Exercised (11,724 ) 3.94 — $ 198 Forfeited (201,456 ) 19.72 — — Outstanding as of December 31, 2019 5,936,239 $ 17.71 9.02 $ 11,873 Exercisable as of December 31, 2019 1,466,625 $ 16.34 8.63 $ 6,124 Vested and expected to vest as of December 31, 2019 5,936,239 $ 17.71 9.02 $ 11,873
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 Nonvested Share Activity	A summary of the changes in the Company’s restricted ordinary shares during the years ended December 31, 2019 and 2018 are as follows and reflect the conversion of ordinary shares in the current and previous years. Number of Weighted average grant date fair value Unvested and outstanding at December 31, 2018 708,834 $ 4.10 Granted 0 0.00 Vested (389,755 ) 4.31 Forfeited (4,335 ) 4.43 Unvested and outstanding at December 31, 2019 314,744 9.05 During the year ended December 31, 2019, the Company granted 500,000 RSUs under the 2018 Plan. The following is a summary of RSU activity for the 2018 Plan for the years ended December 31, 2019 and 2018, respectively: Number of Weighted average Unvested and outstanding at December 31, 2018 — $ — Granted 500,000 12.09 Vested — — Forfeited — — Unvested and outstanding at December 31, 2019 500,000 12.09
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 December 31, Three Months December 31, Years Ended September 30, 2019 2018 2018 2017 Research and development $ 17,761 $ 1,906 $ 3,116 $ 1,145 General and administrative 12,451 1,487 3,649 2,008 Capitalized to fixed assets 174 — — — Total share-based compensation $ 30,386 $ 3,393 $ 6,765 $ 3,153

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Reconciliation of Income Tax Expense (Benefit)	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): Year ended December 31, Three months ended December 31, Year ended September 30, 2019 2018 2018 2017 Net loss before taxes $ (139,008 ) $ (23,253 ) $ (52,031 ) $ (23,380 ) U.K. statutory tax rate 19.0 % 19.0 % 19.0 % 19.5 % Income tax benefit at U.K. statutory tax rate (26,411 ) (4,423 ) (9,886 ) (4,559 ) Tax incentives / credits (16,312 ) (3,234 ) (7,296 ) (3,702 ) Non-deductible expenses 4,048 127 1,553 609 Adjustments in respect of prior years 96 265 (13 ) 13 Operating losses 21,643 3,605 7,317 3,754 Tax on property, plant, equipment and intangibles 267 140 233 113 Other, net 1,510 915 812 119 Total income tax benefit $ (15,159 ) $ (2,605 ) $ (7,280 ) $ (3,653 ) Current income tax benefit (14,749 ) (2,605 ) (7,280 ) (3,653 ) Deferred income tax benefit (410 ) — — — Effective rate of income tax 10.9 % 11.2 % 14.0 % 15.6 %
Schedule of Deferred Tax Assets and Liabilities	Deferred tax assets and liabilities consisted of the following at December 31, 2019 and 2018 (in thousands): December 31, 2019 2018 Deferred tax assets: Other differences $ 1,522 $ 2,870 Tax losses 19,624 7,851 Fixed assets 896 621 Total deferred tax assets 22,042 11,342 Valuation allowances (21,632 ) (11,342 ) Net deferred tax asset (liability) $ 410 $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Assets And Liabilities, Lessee	Leases (in thousands) Balance Sheet Classification As of December 31, 2019 Assets Operating lease assets Operating right-of-use assets $ 23,409 Liabilities Current Operating lease liabilities Current liabilities: Operating lease liabilities $ 2,511 Noncurrent Operating lease liabilities Non-current liabilities: Operating lease liabilities $ 23,710 Total lease liabilities $ 26,221
Lease Cost	Lease cost (in thousands) Statement of Operations Classification Year Ended December 31, 2019 Operating lease cost Operating expenses: research and development $ 3,156 Variable lease cost Operating expenses: research and development 1,222 Operating lease cost Operating expenses: general and administrative 1,241 Variable lease cost Operating expenses: general and administrative 250 Short term lease costs 270 Total lease cost $ 6,139 Other information (in thousands) December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 2,415 Right-of-use assets obtained in exchange for new operating lease liabilities $ 26,124 Weighted-average remaining lease term — operating leases (years) 7.7 Weighted-average discount rate — operating leases 6.8 %
Lease Maturity Schedule	Future fixed payments for non-cancellable operating leases in effect as of December 31, 2019 are payable as follows: Operating Leases Maturity of lease liabilities for the years ending December 31, (in thousands) 2020 4,232 2021 5,039 2022 4,460 2023 4,359 2024 3,869 Thereafter 12,222 Total lease payments 34,181 Less: imputed interest (7,943 ) Less: foreign exchange (gain)/loss (17 ) Present value of lease liabilities 26,221
Future Operating Lease Payments	The following table summarizes the future minimum lease payments due under operating leases as of December 31, 2018 prior to the adoption of ASC 842 (in thousands): Year ending December 31, 2019 $ 2,244 2020 2,332 2021 1,934 2022 1,324 2023 1,196 Thereafter 1,121 Total $ 10,151

Nature of the Business (Details

Nature of the Business (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 27, 2020	Jan. 27, 2020	Apr. 15, 2019	Jun. 26, 2018	Jun. 22, 2018	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Class of Stock
Net loss						$ 20,648	$ 123,849	$ 44,751	$ 19,727	$ 19,727
Accumulated deficit						113,301	237,150
Cash						$ 217,450	$ 210,643	$ 246,984	$ 137,070
Ordinary shares | Subsequent Events
Class of Stock
Number of shares issued in transaction (shares)	7,250,000
Per share price of issuance (usd per share)		$ 11
Ordinary shares | IPO
Class of Stock
Number of shares issued in transaction (shares)				10,147,059	10,147,059
Per share price of issuance (usd per share)				$ 17	$ 17
Proceeds of issuance of ordinary shares, net of issuance costs					$ 156,500
Ordinary shares | Public Stock Offering
Class of Stock
Number of shares issued in transaction (shares)			4,830,000
Per share price of issuance (usd per share)			$ 24
Proceeds of issuance of ordinary shares, net of issuance costs			$ 108,800
Ordinary shares | Public Stock Offering | Subsequent Events
Class of Stock
Number of shares issued in transaction (shares)		7,250,000
Per share price of issuance (usd per share)		$ 11
Proceeds of issuance of ordinary shares, net of issuance costs		$ 75,000
Ordinary shares | Options
Class of Stock
Number of shares issued in transaction (shares)			630,000		1,323,529

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2017
Restricted Cash and Cash Equivalents Items
Restricted cash	$ 787	$ 105	$ 105	$ 0
Letter of credit collateral
Restricted Cash and Cash Equivalents Items
Restricted cash	600
Security deposit
Restricted Cash and Cash Equivalents Items
Restricted cash	$ 200

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Property and Equipment (Details) - USD ($)	Apr. 01, 2019	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment
Fixed asset impairment		$ 0	$ 4,102,000	$ 0	$ 0
Decrease in depreciation expense		$ (645,000)	$ (4,611,000)	$ (1,709,000)	$ (1,009,000)
Increase in basic and diluted net loss per ordinary share (usd per share)		$ (0.52)	$ (2.88)	$ (1.42)	$ (1.43)
Change in fixed asset assumptions
Property, Plant and Equipment
Decrease in depreciation expense			$ 300,000
Increase in basic and diluted net loss per ordinary share (usd per share)			$ 0.01
Office equipment
Property, Plant and Equipment
Property, plant and equipment useful life			3 years
Lab equipment | Minimum
Property, Plant and Equipment
Property, plant and equipment useful life	5 years		5 years
Lab equipment | Maximum
Property, Plant and Equipment
Property, plant and equipment useful life	10 years		10 years
Furniture and fixtures
Property, Plant and Equipment
Property, plant and equipment useful life			5 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Intangible Assets Subject to Amortization (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets
Impairment of finite lived intangible assets	$ 0		$ 0	$ 0
Software
Finite-Lived Intangible Assets
Impairment of finite lived intangible assets		$ 400,000

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Segment Information (Details)	12 Months Ended
	Dec. 31, 2019segmentregion
Accounting Policies [Abstract]
Number of reportable segments | segment	1
Number of geographic regions | region	2

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Research and Development (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Research and development tax credits	$ 37	$ 200	$ 200	$ 200

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Share-Based Compensation (Details)	May 31, 2018	Mar. 31, 2018
Accounting Policies [Abstract]
Probability weighting applied to IPO	80.00%	50.00%

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Foreign Currency Translation (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Foreign currency translation gain (loss)	$ 1,100	$ 4,600	$ 4,000	$ (25)

Summary of Significant Accou_11

Summary of Significant Accounting Policies - Patent Costs (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Patent costs	$ 0.2	$ 2	$ 1	$ 0.5

Summary of Significant Accou_12

Summary of Significant Accounting Policies - Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended			15 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accounting Policies [Abstract]
Foreign currency exchange translation adjustment	$ 5,568	$ (6,797)	$ 6,071	$ (802)	$ (802)

Summary of Significant Accou_13

Summary of Significant Accounting Policies - Schedule of Anti-dilutive Shares (Details) - shares	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares (shares)	4,420,108	6,777,983	2,881,113	1,928,626
Unvested restricted shares and units
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares (shares)	708,834	814,744	815,632	1,358,317
Incentive share options
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive shares (shares)	3,711,274	5,963,239	2,065,481	570,309

Summary of Significant Accou_14

Summary of Significant Accounting Policies - Recent Accounting Pronouncements Adopted (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Accounting Policies [Abstract]
Present value of lease liabilities	$ 26,221	$ 6,300
Right of use asset	$ 23,409	$ 5,600

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Research and development claims receivable	$ 27,567	$ 10,272
Prepayments	7,023	2,069
VAT receivable	1,928	1,973
Other asset	279	0
Grant income receivable	547	661
Other receivable	482	436
Total prepaid expenses and other current assets	$ 37,826	$ 15,411

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment
Less: accumulated depreciation	$ (8,565)	$ (3,708)
Total property and equipment, net	28,164	19,968
Lab equipment
Property, Plant and Equipment
Property and equipment, gross	18,214	10,771
Office equipment
Property, Plant and Equipment
Property and equipment, gross	2,211	1,610
Furniture and fixtures
Property, Plant and Equipment
Property and equipment, gross	1,301	599
Leasehold improvements
Property, Plant and Equipment
Property and equipment, gross	10,316	2,076
Assets under construction
Property, Plant and Equipment
Property and equipment, gross	$ 4,687	$ 8,620

Property and Equipment, Net - D

Property and Equipment, Net - Depreciation (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Depreciation	$ 645	$ 4,611	$ 1,709	$ 1,009

Intangible Asset (Details)

Intangible Asset (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets
Net	$ 254	$ 0
Amortization expense	47
Amortization expense, 2020	104
Amortization expense, 2021	88
Amortization expense, 2022	$ 62
Software license
Finite-Lived Intangible Assets
Estimated Life (years)	3 years
Cost	$ 336
Accumulated Amortization	(82)
Net	$ 254

Accrued Expenses and Other Li_3

Accrued Expenses and Other Liabilities (Details) $ in Thousands, £ in Millions	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Mar. 31, 2018GBP (£)
Payables and Accruals [Abstract]
Compensation and benefits	$ 6,568	$ 3,296
Research and development costs	10,449	9,362
UCLB milestone	663	638	£ 0.5
Professional fees	2,611	4,130
Deferred rent		561
Corporate tax	391	620
Other liabilities	716	447
Total accrued expenses and other liabilities	21,398	19,054
Current portion of long term debt and leases	$ 300	$ 400

Shareholders_ Equity - Ordinary

Shareholders’ Equity - Ordinary Shares (Details)	Dec. 31, 2019£ / sharesshares	Dec. 31, 2019$ / sharesshares	Dec. 31, 2018£ / sharesshares	Dec. 31, 2018$ / sharesshares	Jun. 26, 2018USD ($)
Ordinary shares
Class of Stock
Maximum nominal shares authorized for grant | $					$ 8,400
Common stock, shares, issued (shares)	44,983,006	44,983,006	40,145,617	40,145,617
Common stock, par value (usd/gbp per share) | $ / shares		$ 0.000042		$ 0.000042
Deferred Shares
Class of Stock
Common stock, shares, issued (shares)	34,425	34,425	0	0
Common stock, par value (usd/gbp per share) | £ / shares	£ 0.00001		£ 0.00001
Deferred B shares
Class of Stock
Common stock, shares, issued (shares)	88,893,548	88,893,548	0	0
Common stock, par value (usd/gbp per share) | £ / shares	£ 0.00099		£ 0.00099
Deferred C shares
Class of Stock
Common stock, shares, issued (shares)	1	1	0	0
Common stock, par value (usd/gbp per share) | £ / shares	£ 0.000008		£ 0.000008

Shareholders_ Equity - Initial

Shareholders’ Equity - Initial Public Offering and Impact of Corporate Reorganization (Details)	Jun. 26, 2018USD ($)$ / sharesshares	Jun. 22, 2018USD ($)$ / sharesshares	Dec. 31, 2018USD ($)shares	Dec. 31, 2019USD ($)shares	Sep. 30, 2018USD ($)shares	Sep. 30, 2017USD ($)shares	Jun. 22, 2018GBP (£)shares
Class of Stock
Proceeds of issuance of ordinary shares, net of issuance costs			$ 0	$ 108,863,000	$ 156,920,000	$ 127,686,000
Payment of stock issuance cost	$ 16,000,000
Equity conversion ratio		3.185
Shares outstanding (shares) | shares			129,073,591	133,910,980	129,074,156	29,962,741
Ordinary shares
Class of Stock
Shares outstanding (shares) | shares			40,145,617	44,983,006	40,146,182
Shares value			$ 2,000	$ 2,000
Ordinary shares | IPO
Class of Stock
Number of shares issued in transaction (shares) | shares	10,147,059	10,147,059
Per share price of issuance (usd per share) | $ / shares	$ 17	$ 17
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	34,425		34,425
Shares value		$ 1	$ 0	$ 0
Deferred B shares
Class of Stock
Shares outstanding (shares) | shares		88,893,548	88,893,548	88,893,548	88,893,548		88,893,548
Shares value		$ 118,000	$ 118,000	$ 118,000
Share capital registration threshold | £							£ 50,000
Deferred C shares
Class of Stock
Shares outstanding (shares) | shares			1	1	1
Shares value		$ 1	$ 0	$ 0

Shareholders_ Equity (Details)

Shareholders’ Equity (Details) - shares	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 22, 2018	Sep. 30, 2017
Class of Stock
Total ordinary and Deferred shares (shares)	133,910,980	129,073,591	129,074,156		29,962,741
Series A preferred shares
Class of Stock
Total ordinary and Deferred shares (shares)					24,490,705
Class B ordinary shares
Class of Stock
Total ordinary and Deferred shares (shares)					3,375,196
Class C ordinary shares
Class of Stock
Total ordinary and Deferred shares (shares)					2,096,840
Ordinary shares
Class of Stock
Total ordinary and Deferred shares (shares)	44,983,006	40,145,617	40,146,182
Deferred Shares
Class of Stock
Total ordinary and Deferred shares (shares)	34,425	34,425	34,425	34,425
Deferred B shares
Class of Stock
Total ordinary and Deferred shares (shares)	88,893,548	88,893,548	88,893,548	88,893,548
Deferred C Shares
Class of Stock
Total ordinary and Deferred shares (shares)	1	1	1

Share Based Compensation - 2018

Share Based Compensation - 2018 Equity Incentive Plan (Narratives) (Details) - shares	1 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2019
Stock options
Share-based Compensation Arrangement by Share-based Payment Award
Share based compensation term (years)		10 years
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)		3 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 One | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting percentage		50.00%
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
Vesting Group Two | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting percentage		50.00%
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	6,686,764
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 - Opti

Share Based Compensation - Options Valuation Assumptions (Details) - Stock options	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	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 28 days	6 years 28 days	6 years 28 days
Risk-free interest rate minimum (percentage)	1.39%	2.70%	2.61%	1.91%
Risk-free interest rate maximum (percentage)	2.66%	3.09%	3.00%	2.05%
Expected volatility minimum (percentage)	72.30%	69.52%	68.15%	68.61%
Expected volatility maximum (percentage)	76.22%	71.26%	72.99%	68.93%
Expected dividend yield (percentage)	0.00%	0.00%	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Expected term (in years)	5 years 3 months 7 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Expected term (in years)	6 years 28 days

Share Based Compensation - Shar

Share Based Compensation - Share Options Rollforward (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding
Beginning balance (shares)		3,711,274
Granted (shares)		2,438,145
Exercised (shares)		(11,724)
Forfeited (shares)		(201,456)
Ending balance (shares)		5,936,239	3,711,274
Shares Exercisable (shares)	1,466,625
Vested and expected to vest (shares)		5,936,239
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price
Beginning balance (weighted average exercise price)		$ 19.25
Granted (weighted average exercise price)		15.22
Exercised (weighted average exercise price)		3.94
Forfeited (weighted average exercise price)		19.72
Ending balance (weighted average exercise price)		17.71	$ 19.25
Exercisable (weighted average exercise price)	$ 16.34
Vested or expected to vest (weighted average exercise price)		$ 17.71
Options outstanding (weighted- average remaining contractual term years)		9 years 7 days	9 years 5 months 19 days
Options exercisable (weighted- average remaining contractual term years)	8 years 7 months 17 days
Vested and expected to vest (weighted- average remaining contractual term years)		9 years 7 days
Options outstanding (aggregate intrinsic value)		$ 11,873	$ 51,464
Exercised (aggregate intrinsic value)		198
Options exercisable (aggregate intrinsic value)	$ 6,124
Options vested and expected to vest (aggregate intrinsic value)		$ 11,873

Share Based Compensation - Sh_2

Share Based Compensation - Share Options (Narratives) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award
Unrecognized stock based compensation		$ 34
Weighted average vesting period		3 years 4 months 24 days
Stock options
Share-based Compensation Arrangement by Share-based Payment Award
Weighted average grant date fair value (usd per share)	$ 20.04	$ 10.07	$ 8.55	$ 4.04

Share Based Compensation - Rest

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 - Re_2

Share Based Compensation - Restricted Ordinary Shares Rollforward (Details) - Restricted Ordinary Shares	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Number of restricted shares
Unvested and outstanding beginning balance (shares) | shares	708,834
Granted (shares) | shares	0
Vested (shares) | shares	(389,755)
Forfeited (shares) | shares	(4,335)
Unvested and outstanding ending balance (shares) | shares	314,744
Weighted average grant date fair value
Unvested and outstanding beginning balance (weighted average grant date fair value) | $ / shares	$ 4.10
Granted (weighted average grant date fair value) | $ / shares	0
Vested (weighted average grant date fair value) | $ / shares	4.31
Forfeited (weighted average grant date fair value) | $ / shares	4.43
Unvested and outstanding ending balance (weighted average grant date fair value) | $ / shares	$ 9.05

Share Based Compensation - Re_3

Share Based Compensation - Restricted Ordinary Shares (Narratives) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Share-based Compensation Arrangement by Share-based Payment Award
Weighted average vesting period	3 years 4 months 24 days
Restricted Ordinary Shares
Share-based Compensation Arrangement by Share-based Payment Award
Unrecognized stock based compensation	$ 0.3
Weighted average vesting period	1 year 6 months

Share Based Compensation - Re_4

Share Based Compensation - Restricted Stock Unites (Narratives) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award
Weighted average vesting period	3 years 4 months 24 days
Vesting Group One
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
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award
Granted (shares) | shares	500,000
Vesting period (years)	3 years
Unrecognized stock based compensation | $	$ 5.9
Weighted average vesting period	3 years
Restricted stock units | Vesting Group One
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting percentage	50.00%
Restricted stock units | Vesting Group Two
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting percentage	50.00%

Share Based Compensation - Re_5

Share Based Compensation - Restricted Stock Units Rollforward (Details) - Restricted stock units	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Number of restricted shares
Unvested and outstanding beginning balance (shares) | shares	0
Granted (shares) | shares	500,000
Vested (shares) | shares	0
Forfeited (shares) | shares	0
Unvested and outstanding ending balance (shares) | shares	500,000
Weighted average grant date fair value
Unvested and outstanding beginning balance (weighted average grant date fair value) | $ / shares	$ 0
Granted (weighted average grant date fair value) | $ / shares	12.09
Vested (weighted average grant date fair value) | $ / shares	0
Forfeited (weighted average grant date fair value) | $ / shares	0
Unvested and outstanding ending balance (weighted average grant date fair value) | $ / shares	$ 12.09

Share Based Compensation - Comp

Share Based Compensation - Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award
Total share-based compensation	$ 3,393	$ 30,386	$ 6,765	$ 3,153
Research and development
Share-based Compensation Arrangement by Share-based Payment Award
Total share-based compensation	1,906	17,761	3,116	1,145
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award
Total share-based compensation	1,487	12,451	3,649	2,008
Capitalized to fixed assets
Share-based Compensation Arrangement by Share-based Payment Award
Total share-based compensation	$ 0	$ 174	$ 0	$ 0

License Agreements (Details)

License Agreements (Details) £ in Thousands, $ in Thousands	1 Months Ended
	Mar. 31, 2018GBP (£)	Mar. 31, 2016USD ($)shares	Sep. 30, 2014shares	Dec. 31, 2019USD ($)	Dec. 31, 2019GBP (£)	Dec. 31, 2018USD ($)
Schedule Of License Agreements
Accrued license fees payable	£ 500			$ 663		$ 638
UCLB
Schedule Of License Agreements
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
Conditional payment					35,500
UCLB | Net Sales Levels
Schedule Of License Agreements
Conditional payment					51,000
UCLB | Product Sales
Schedule Of License Agreements
Conditional payment					18,000
UCLB | Product Sales | Minimum
Schedule Of License Agreements
Conditional payment					1,000
UCLB | Product Sales | Maximum
Schedule Of License Agreements
Conditional payment					£ 18,500

Income Taxes - (Narratives) (De

Income Taxes - (Narratives) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income tax benefit	$ 2,605	$ 15,159	$ 7,280	$ 3,653
Increase in deferred tax assets		10,700
Deferred tax asset	0	410
Operating loss carryforward, foreign		115,400
Deferred tax asset valuation allowances	$ 11,342	$ 21,632

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Net loss before taxes	$ (23,253)	$ (139,008)	$ (52,031)	$ (23,380)
U.K. statutory tax rate (percentage)	19.00%	19.00%	19.00%	19.50%
Income tax benefit at U.K. statutory tax rate	$ (4,423)	$ (26,411)	$ (9,886)	$ (4,559)
Tax incentives / credits	(3,234)	(16,312)	(7,296)	(3,702)
Non-deductible expenses	127	4,048	1,553	609
Adjustments in respect of prior years	265	96	(13)	13
Operating losses	3,605	21,643	7,317	3,754
Tax on property, plant, equipment and intangibles	140	267	233	113
Other, net	915	1,510	812	119
Total income tax benefit	(2,605)	(15,159)	(7,280)	(3,653)
Current income tax benefit	(2,605)	(14,749)	(7,280)	(3,653)
Deferred income tax benefit	$ 0	$ (410)	$ 0	$ 0
Effective rate of income tax (percentage)	11.20%	10.90%	14.00%	15.60%

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Other differences	$ 1,522	$ 2,870
Tax losses	19,624	7,851
Fixed assets	896	621
Total deferred tax assets	22,042	11,342
Valuation allowances	(21,632)	(11,342)
Net deferred tax asset (liability)	$ 410	$ 0

Commitments and Contingencies -

Commitments and Contingencies - (Narratives) (Details) $ in Thousands	1 Months Ended		3 Months Ended	12 Months Ended
	Oct. 31, 2018	Sep. 30, 2017	Dec. 31, 2018USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2019unit	Jan. 31, 2019	Jan. 01, 2019USD ($)
Loss Contingencies
Operating lease assets				$ 23,409					$ 5,600
Minimum lease payments for leases signed but not yet commenced				$ 57,900
Rent expense			$ 500		$ 900	$ 600
Imperial (Forest House) Limited | Building
Loss Contingencies
Lease term (in years)				10 years
Imperial (Forest House) Limited | Additional Space
Loss Contingencies
Lease term (in years)				15 months
Catapult Manufacturing Center | Building
Loss Contingencies
Rent free period (in months)		6 months
Laboratory Space In White City, London | Building
Loss Contingencies
Lease term (in years)					10 years
Operating lease assets				$ 8,200
Manufacturing Space In Enfield, United Kingdom | Building
Loss Contingencies
Lease term (in years)					15 years
Leasehold Improvements				4,100
Number of units (units) | unit							3
Office Space In Rockville, Maryland | Building
Loss Contingencies
Operating lease rent free period	4 months
Office And Manufacturing Space in Rockville, Maryland | Building
Loss Contingencies
Lease term (in years)								16 years
Leasehold Improvements				2,200
Minimum lease payments for leases signed but not yet commenced				57,900
Software license
Loss Contingencies
Loss contingency accrual				$ 700

Commitments and Contingencies_2

Commitments and Contingencies - Lease Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Assets
Operating lease assets	$ 23,409	$ 5,600
Current
Lease liability	2,511
Noncurrent
Operating lease liabilities	23,710
Total lease liabilities	$ 26,221	$ 6,300

Commitments and Contingencies_3

Commitments and Contingencies - Lease Costs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Lease, Cost
Short term lease costs	$ 270
Total lease cost	6,139
Research and development
Lease, Cost
Operating lease cost	3,156
Variable lease cost	1,222
General and administrative
Lease, Cost
Operating lease cost	1,241
Variable lease cost	$ 250

Commitments and Contingencies_4

Commitments and Contingencies - Other Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 2,415
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 26,124
Weighted-average remaining lease term — operating leases (years)	7 years 8 months 12 days
Weighted-average discount rate — operating leases (percent)	6.80%

Commitments and Contingencies_5

Commitments and Contingencies - Lease Maturity Schedule (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Maturity of lease liabilities for the years ending December 31,
2020	$ 4,232
2021	5,039
2022	4,460
2023	4,359
2024	3,869
Thereafter	12,222
Total lease payments	34,181
Less: imputed interest	(7,943)
Less: foreign exchange (gain)/loss	(17)
Present value of lease liabilities	$ 26,221	$ 6,300

Commitments and Contingencies_6

Commitments and Contingencies - Future Minimum Lease Payment - Before Adoption (Details) $ in Thousands	Dec. 31, 2018USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity
2019	$ 2,244
2020	2,332
2021	1,934
2022	1,324
2023	1,196
Thereafter	1,121
Total	$ 10,151

Employee Benefit Plans (Details

Employee Benefit Plans (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Sep. 30, 2017
Retirement Benefits [Abstract]
Employer contributions to defined benefit pension schemes	$ 200,000	$ 1,000,000	$ 500,000	$ 300,000
Employer contribution (percent)		4.00%
Employer contributions	$ 18,000	$ 200,000	$ 0	$ 0

Subsequent Events (Details)

Subsequent Events (Details) $ / shares in Units, $ in Thousands	Feb. 27, 2020USD ($)ft²shares	Dec. 31, 2018USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Jan. 27, 2020$ / shares
Subsequent Event
Proceeds of issuance of ordinary shares, net of issuance costs		$ 0	$ 108,863	$ 156,920	$ 127,686
Subsequent Events | Office Space in Rockville, Maryland
Subsequent Event
Area of property (sqft) | ft²	27,502
Subsequent Events | Ordinary shares
Subsequent Event
Number of shares issued in transaction (shares) | shares	7,250,000
Per share price of issuance (usd per share) | $ / shares						$ 11
Proceeds of issuance of ordinary shares, net of issuance costs	$ 75,000

Uncategorized Items - autl-2019

Label	Element	Value
Stock Issued During Period, Value, New Issues	us-gaap_StockIssuedDuringPeriodValueNewIssues	$ 127,686,000
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	3,153,000
AOCI Attributable to Parent [Member]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent	us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent	802,000
Retained Earnings [Member]
Net Income (Loss) Attributable to Parent	us-gaap_NetIncomeLoss	(19,727,000)
Additional Paid-in Capital [Member]
Stock Issued During Period, Value, New Issues	us-gaap_StockIssuedDuringPeriodValueNewIssues	127,685,000
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	3,153,000
Ordinary Shares [Member] | Common Stock [Member]
Stock Issued During Period, Value, New Issues	us-gaap_StockIssuedDuringPeriodValueNewIssues	$ 1,000
Stock Issued During Period, Shares, New Issues	us-gaap_StockIssuedDuringPeriodSharesNewIssues	16,041,198