Entity Central Index Key
Marketable securities fair value disclosure.
Finite lived intangible assets amortization expense after year four.
Long term debt maturities repayments of principal after year four.
Unamortized portion of final payment.
Cover [Abstract]
Document Type
Document Type
Amendment Flag
Amendment Flag
Document Period End Date
Document Period End Date
Document Fiscal Year Focus
Document Fiscal Year Focus
Document Fiscal Period Focus
Document Fiscal Period Focus
Entity Registrant Name
Entity Registrant Name
Current Fiscal Year End Date
Current Fiscal Year End Date
Entity Central Index Key
Entity Central Index Key
Entity Filer Category
Entity Filer Category
Entity Small Business
Entity Small Business
Entity Common Stock, Shares Outstanding
Entity Common Stock Shares Outstanding
Entity Shell Company
Entity Shell Company
Entity Current Reporting Status
Entity Current Reporting Status
Entity Interactive Data Current
Entity Interactive Data Current
Entity Incorporation, State or Country Code
Entity Incorporation State Country Code
Entity Address, Address Line One
Entity Address Address Line1
Entity Address, City or Town
Entity Address City Or Town
Entity Address, Postal Zip Code
Entity Address Postal Zip Code
City Area Code
City Area Code
Local Phone Number
Local Phone Number
Document Quarterly Report
Document Quarterly Report
Document Transition Report
Document Transition Report
Entity File Number
Entity File Number
Entity Emerging Growth Company
Entity Emerging Growth Company
Entity Tax Identification Number
Entity Tax Identification Number
Entity Address, Country
Entity Address Country
Title of 12(b) Security
Security12b Title
Trading Symbol
Trading Symbol
Security Exchange Name
Security Exchange Name
Entity Bankruptcy Proceedings, Reporting Current
Entity Bankruptcy Proceedings Reporting Current
Research and development tax credit receivable, current.
Research and development tax credit receivable, noncurrent.
The amount of accrued expenses and other current liabilities.
Statement Of Financial Position [Abstract]
Assets
Assets [Abstract]
Current assets:
Assets Current [Abstract]
Cash and cash equivalents
Cash And Cash Equivalents At Carrying Value
Marketable securities
Marketable Securities
Accounts receivable
Accounts Receivable Net Current
Prepaid expenses and other current assets
Prepaid Expense And Other Assets Current
Research and development tax credit receivable, current
Research And Development Tax Credit Receivable Current
Total current assets
Assets Current
Non-current assets:
Assets Noncurrent [Abstract]
Operating lease right-of-use-assets
Operating Lease Right Of Use Asset
Property and equipment, net
Property Plant And Equipment Net
Research and development tax credit receivable
Research And Development Tax Credit Receivable Noncurrent
Restricted cash
Restricted Cash And Cash Equivalents Noncurrent
Intangible assets, net
Intangible Assets Net Excluding Goodwill
Other assets
Other Assets Noncurrent
Total assets
Assets
Liabilities and shareholders’ equity
Liabilities And Stockholders Equity [Abstract]
Current liabilities:
Liabilities Current [Abstract]
Accounts payable
Accounts Payable Current
Accrued expenses and other current liabilities
Accrued Expenses And Other Current Liabilities
Deferred revenue
Deferred Revenue Current
Operating lease liabilities
Operating Lease Liability Current
Notes payable, current
Notes Payable Current
Total current liabilities
Liabilities Current
Notes payable, long-term
Long Term Notes Payable
Deferred revenue, net of current portion
Deferred Revenue Noncurrent
Operating lease liabilities, net of current portion
Operating Lease Liability Noncurrent
Other long-term liabilities
Other Liabilities Noncurrent
Total liabilities
Liabilities
Commitments and contingencies (see Note 13)
Commitments And Contingencies
Shareholders’ equity:
Stockholders Equity [Abstract]
Ordinary shares, £0.10 nominal value; 124,770,519 and 98,283,603 ordinary shares issued and outstanding at September 30, 2021 and December 31, 2020, respectively; 715,434 and nil non-voting ordinary shares issued and outstanding at September 30, 2021 and December 31, 2020, respectively
Common Stock Value
Additional paid-in capital
Additional Paid In Capital
Accumulated other comprehensive income
Accumulated Other Comprehensive Income Loss Net Of Tax
Accumulated deficit
Retained Earnings Accumulated Deficit
Total shareholders’ equity
Stockholders Equity
Total liabilities and shareholders’ equity
Liabilities And Stockholders Equity
Statement [Table]
Statement [Table]
Class of Stock
Statement Class Of Stock [Axis]
Class of Stock
Class Of Stock [Domain]
Non-voting ordinary shares.
Non-voting Ordinary Shares
Non Voting Ordinary Shares [Member]
Statement [Line Items]
Statement [Line Items]
Ordinary Shares, Nominal Value
Common Stock Par Or Stated Value Per Share
Ordinary Shares, Issued
Common Stock Shares Issued
Ordinary Shares, Outstanding
Common Stock Shares Outstanding
Income Statement [Abstract]
Product and Service
Product Or Service [Axis]
Product and Service
Products And Services [Domain]
Product Sales, Net [Member]
Product [Member]
Collaboration.
Collaboration Revenue [Member]
Collaboration [Member]
Total revenues
Revenue From Contract With Customer Excluding Assessed Tax
Costs and operating expenses:
Operating Costs And Expenses [Abstract]
Cost of product sales
Cost Of Goods And Services Sold
Cost, Product and Service [Extensible List]
Type Of Cost Good Or Service Extensible List
Research and development
Research And Development Expense
Selling, general and administrative
Selling General And Administrative Expense
Total costs and operating expenses
Costs And Expenses
Loss from operations
Operating Income Loss
Other (expense) income:
Nonoperating Income Expense [Abstract]
Interest income
Investment Income Interest
Interest expense
Interest Expense
Other (expense) income, net
Other Nonoperating Income Expense
Total other (expense) income, net
Nonoperating Income Expense
Net loss before income tax
Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest
Income tax benefit (expense)
Income Tax Expense Benefit
Net loss
Net Income Loss
Other comprehensive income (loss)
Other Comprehensive Income Loss Tax [Abstract]
Foreign currency translation adjustment
Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax
Unrealized gain (loss) on marketable securities
Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax
Total other comprehensive income (loss)
Other Comprehensive Income Loss Net Of Tax
Total comprehensive loss
Comprehensive Income Net Of Tax
Net loss per share, basic and diluted
Earnings Per Share Basic And Diluted
Weighted average number of ordinary shares outstanding, basic and diluted
Weighted Average Number Of Share Outstanding Basic And Diluted
Non-cash interest expense.
Non-cash consideration for license.
Asset acquisition liability amortization of loss provisions.
Amortization of premium on marketable securities.
Increase (decrease) in research and development tax credit receivable.
Increase decrease in operating leases, right-of-use-assets
Increase decrease in accounts payable and accrued liabilities and other operating liabilities.
Increase decrease in operating lease liabilities
Receipt of funds from construction deposit.
Proceeds from issuance of shares as part of collaboration agreement.
Statement Of Cash Flows [Abstract]
Cash flows from operating activities:
Net Cash Provided By Used In Operating Activities [Abstract]
Net loss
Profit Loss
Adjustments to reconcile net loss to net cash used in operating activities:
Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract]
Depreciation and amortization
Depreciation Depletion And Amortization
Non-cash share-based compensation
Share Based Compensation
Impairment of long-lived assets
Asset Impairment Charges
Non-cash interest expense
Non Cash Interest Expense
Non-cash consideration for licenses
Non Cash Consideration For License
Amortization of Strimvelis loss provision
Asset Acquisition Liability Amortization Of Loss Provisions
Amortization of premium on marketable securities
Amortization Of Premium On Marketable Securities
Deferred income taxes
Deferred Income Tax Expense Benefit
Unrealized foreign currency
Foreign Currency Transaction Gain Loss Unrealized
Changes in operating assets and liabilities:
Increase Decrease In Operating Capital [Abstract]
Accounts receivable
Increase Decrease In Accounts Receivable
Research and development tax credit receivable
Increase Decrease In Research And Development Tax Credit Receivable
Prepaid expenses, other current assets and other assets
Increase Decrease In Prepaid Deferred Expense And Other Assets
Operating leases, right-of-use assets
Increase Decrease In Operating Right Of Use Assets
Accounts payable, accrued expenses and other current liabilities
Increase Decrease In Accounts Payable And Accrued Liabilities And Other Operating Liabilities
Deferred revenue
Increase Decrease In Contract With Customer Liability
Operating lease liabilities
Increase Decrease In Operating Lease Liabilities
Net cash used in operating activities
Net Cash Provided By Used In Operating Activities
Cash flows from investing activities:
Net Cash Provided By Used In Investing Activities [Abstract]
Proceeds from sales and maturities of marketable securities
Proceeds From Sale And Maturity Of Marketable Securities
Purchases of marketable securities
Payments To Acquire Available For Sale Securities Debt
Payment of construction deposit
Payments To Acquire Restricted Certificates Of Deposit
Receipt of funds from construction deposit
Receipt Of Funds From Construction Deposit
Payments on intangible assets
Payments To Acquire Intangible Assets
Purchases of property and equipment
Payments To Acquire Property Plant And Equipment
Net cash (used in) provided by investing activities
Net Cash Provided By Used In Investing Activities
Cash flows from financing activities:
Net Cash Provided By Used In Financing Activities [Abstract]
Proceeds from modification of credit facility, net of debt issuance costs paid
Proceeds From Issuance Of Debt
Proceeds from employee equity plans
Proceeds From Stock Plans
Proceeds from issuance of shares as part of collaboration agreement
Proceeds From Issuance Of Shares As Part Of Collaboration Agreement
Proceeds from the issuance of ordinary shares in private placement
Proceeds From Issuance Of Private Placement
Payment of placement agent fees and offering costs
Payments Of Stock Issuance Costs
Net cash provided by financing activities
Net Cash Provided By Used In Financing Activities
Effect of exchange rate changes on cash, cash equivalents, and restricted cash
Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations
Net increase in cash, cash equivalents and restricted cash
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect
Cash, cash equivalents, and restricted cash, beginning of period
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations
Cash, cash equivalents, and restricted cash, end of period
Supplemental disclosure of non-cash operating, investing and financing activities
Noncash Investing And Financing Items [Abstract]
Property, equipment and intangibles in accounts payable and accrued expenses
Capital Expenditures Incurred But Not Yet Paid
Lease assets obtained in exchange for new operating lease liabilities
Right Of Use Asset Obtained In Exchange For Operating Lease Liability
Shares issued as part of license agreement
Stock Issued1
Supplemental disclosure of cash flow information:
Supplemental Cash Flow Information [Abstract]
Cash paid for taxes
Income Taxes Paid Net
Cash paid for interest
Interest Paid Net
Stock issued during period shares exercise of share options and employee stock purchase plan.
Stock issued during period value exercise of share options and employee stock purchase plan.
Stock issued during period shares as part of collaboration agreement.
Stock issued during period value as part of collaboration agreement.
Statement Of Stockholders Equity [Abstract]
Equity Components
Statement Equity Components [Axis]
Equity Component
Equity Component [Domain]
Ordinary Shares
Common Stock [Member]
Additional Paid-In Capital
Additional Paid In Capital [Member]
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income [Member]
Accumulated Deficit
Retained Earnings [Member]
Balance
Balance, Shares
Shares Outstanding
Share-based compensation expense
Stock Issued During Period Value Share Based Compensation
Exercise of share options
Stock Issued During Period Value Stock Options Exercised
Exercise of share options, Shares
Stock Issued During Period Shares Stock Options Exercised
Exercise of share options and issuance of ESPP shares
Stock Issued During Period Value Exercise Of Share Options And Employee Stock Purchase Plan
Exercise of share options and issuance of ESPP shares, shares
Stock Issued During Period Shares Exercise Of Share Options And Employee Stock Purchase Plan
Ordinary shares issued as part of license agreements
Stock Issued During Period Value Issued For Services
Ordinary shares issued as part of license agreements, Shares
Stock Issued During Period Shares Issued For Services
Vesting of restricted share units, net of shares withheld for taxes
Restricted Stock Value Shares Issued Net Of Tax Withholdings
Vesting of restricted share units, net of shares withheld for taxes, shares
Restricted Stock Shares Issued Net Of Shares For Tax Withholdings
Sale of voting and non-voting ordinary shares, net of issuance costs
Stock Issued During Period Value New Issues
Sale of voting and non-voting ordinary shares, net of issuance costs, Shares
Stock Issued During Period Shares New Issues
Issuance costs associated with sale of voting and non-voting ordinary shares
Adjustments To Additional Paid In Capital Stock Issued Issuance Costs
Issuance of shares as part of collaboration agreement
Stock Issued During Period Value As Part Of Collaboration Agreement
Issuance of shares as part of collaboration agreement, shares
Stock Issued During Period Shares As Part Of Collaboration Agreement
Foreign currency translation
Unrealized gain (loss) on marketable securities
Marketable Securities Unrealized Gain Loss
Net loss
Balance
Balance, Shares
Sale of voting and non-voting ordinary shares, issuance costs
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of the Business
Business Description And Basis Of Presentation [Text Block]
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies
Significant Accounting Policies [Text Block]
Fair Value Disclosures [Abstract]
Fair Value Measurements and Marketable Securities
Fair Value Disclosures [Text Block]
Prepaid expenses and other current assets.
Prepaid Expense And Other Assets Current [Abstract]
Prepaid Expenses and Other Current Assets
Prepaid Expenses And Other Current Assets [Text Block]
Property Plant And Equipment [Abstract]
Property and Equipment, Net
Property Plant And Equipment Disclosure [Text Block]
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible Assets, Net
Intangible Assets Disclosure [Text Block]
Other Assets Noncurrent Disclosure [Abstract]
Other Assets
Other Assets Disclosure [Text Block]
Accrued Liabilities And Other Liabilities [Abstract]
Accrued Expenses and Other Current Liabilities
Accounts Payable Accrued Liabilities And Other Liabilities Disclosure Current [Text Block]
Debt Disclosure [Abstract]
Notes Payable
Debt Disclosure [Text Block]
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation
Disclosure Of Compensation Related Costs Share Based Payments [Text Block]
Restructuring And Related Activities [Abstract]
Restructuring Charges
Restructuring And Related Activities Disclosure [Text Block]
License Agreements.
License agreements.
License Agreements [Abstract]
License Agreements
License Agreements Disclosure [Text Block]
Collaborative arrangement.
Collaborative Arrangement [Abstract]
Collaboration Agreement with Pharming Group N.V.
Collaborative Arrangement Disclosure [Text Block]
Income Tax Disclosure [Abstract]
Income Taxes
Income Tax Disclosure [Text Block]
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies
Commitments And Contingencies Disclosure [Text Block]
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans
Pension And Other Postretirement Benefits Disclosure [Text Block]
Related Party Transactions [Abstract]
Related Party Transactions
Related Party Transactions Disclosure [Text Block]
Basis of presentation
Basis Of Accounting Policy Policy [Text Block]
Use of estimates
Use Of Estimates
Foreign currency
Foreign Currency Transactions And Translations Policy [Text Block]
Cash and cash equivalents
Cash And Cash Equivalents Policy [Text Block]
Marketable securities
Marketable Securities Policy
Research and development income tax credits.
United Kingdom research and development tax credits
Research And Development Income Tax Credits Policy [Text Block]
Restricted cash and construction deposits
Cash And Cash Equivalents Restricted Cash And Cash Equivalents Policy
Intangible assets, net
Intangible Assets Finite Lived Policy
Product sales
Revenue From Contract With Customer Policy [Text Block]
Research and development costs
Research And Development Expense Policy
Research agreement cost and accrual.
Research agreement costs and accruals
Research Agreement Cost And Accrual Policy
Share-based compensation
Compensation Related Costs Policy [Text Block]
Comprehensive loss
Comprehensive Income Policy Policy [Text Block]
Leases
Lessee Leases Policy [Text Block]
Impairment of long-lived assets
Impairment Or Disposal Of Long Lived Assets Policy [Text Block]
Strimvelis loss provision.
Strimvelis loss provision
Strimvelis Loss Provision Policy [Text Block]
Net loss per share
Earnings Per Share Policy [Text Block]
Recently adopted accounting pronouncements
New Accounting Pronouncements Policy Policy [Text Block]
Summary of Amounts Recognized to Offset Research and Development Expense
Summary Of Tax Credit Carryforwards [Text Block]
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash
Schedule Of Restricted Cash And Cash Equivalents [Text Block]
Schedule of changes in loss provision.
Schedule of Changes in Loss Provision
Schedule Of Changes In Loss Provision Table [Text Block]
Securities Excluded in the Computation of Diluted Net Loss Per Ordinary Share
Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Schedule of Cash Equivalents and Marketable Securities
Schedule Of Cash Cash Equivalents And Short Term Investments Table [Text Block]
Schedule of Marketable Securities
Schedule Of Available For Sale Securities Reconciliation Table [Text Block]
Schedule of Available-for-Sale Debt Securities by Contractual Maturity
Investments Classified By Contractual Maturity Date Table [Text Block]
Schedule of Prepaid Expenses and Other Current Assets
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Text Block]
Schedule of Property and Equipment, Net
Property Plant And Equipment [Text Block]
Schedule of intangible assets net of accumulated amortization.
Schedule of Intangible Assets Net of Accumulated Amortization
Schedule Of Intangible Assets Net Of Accumulated Amortization Table [Text Block]
Schedule of Estimated Future Amortization For Intangible Assets
Scheduleof Finite Lived Intangible Assets Future Amortization Expense Table [Text Block]
Schedule of Other Assets
Schedule Of Other Assets Noncurrent [Text Block]
Schedule of Accrued Expenses and Other Current Liabilities
Schedule Of Accrued Liabilities Table [Text Block]
Summary of Notes Payable
Schedule Of Debt Table [Text Block]
Summary of Estimated Future Principal Payments Due
Schedule Of Maturities Of Long Term Debt Table [Text Block]
Summary of Option Activity
Schedule Of Share Based Compensation Stock Options Activity Table [Text Block]
Summary of Award Activity
Schedule Of Share Based Compensation Restricted Stock Units Award Activity Table [Text Block]
Share-based Compensation Expense
Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Text Block]
Summary of Cash Restructuring Charges
Schedule Of Restructuring And Related Costs [Text Block]
Summary of Impairment of Long Lived Assets
Details Of Impairment Of Long Lived Assets Held And Used By Asset [Text Block]
Summary of Research and Development Costs Incurred and Collaboration Revenue Recognized
Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions Table [Text Block]
Schedule of Annual Commitments Associated with the Contract
Contractual Obligation Fiscal Year Maturity Schedule Table [Text Block]
Closing price of share date.
Payments of other issuance costs.
Net proceeds from issuance of private placement.
Organization consolidation and presentation of financial statements.
Organization consolidation and presentation of financial statements.
Organization Consolidation And Presentation Of Financial Statements [Table]
Organization Consolidation And Presentation Of Financial Statements [Table]
Collaborative Arrangement and Arrangement Other than Collaborative
Type Of Arrangement [Axis]
Collaborative Arrangement and Arrangement Other than Collaborative
Arrangements And Nonarrangement Transactions [Member]
Securities purchase agreement.
Securities Purchase Agreement
Securities Purchase Agreement [Member]
Sale of Stock
Subsidiary Sale Of Stock [Axis]
Sale of Stock
Sale Of Stock Name Of Transaction [Domain]
Private Placement
Private Placement [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of ordinary shares issued and sold
Nominal value of shares issued and sold
Purchase price per share
Sale Of Stock Price Per Share
Closing price of share date
Closing Price Of Share Date
Placement agent fees
Other issuance costs
Payments Of Other Issuance Costs
Private placement, transaction date
Sale Of Stock Transaction Date
Net proceeds from private placement
Net Proceeds From Issuance Of Private Placement
Accumulated deficit
Cash, cash equivalents and marketable securities
Cash Cash Equivalents And Short Term Investments
Summary of significant accounting policies.
Summary Of Significant Accounting Policies [Abstract]
Summary of significant accounting policies.
Summary of significant accounting policies.
Summary Of Significant Accounting Policies [Table]
Summary Of Significant Accounting Policies [Table]
Geographical
Statement Geographical [Axis]
Geographical
Segment Geographical [Domain]
United Kingdom
G B
Lease Contractual Term
Lease Contractual Term [Axis]
Lease Contractual Term
Lease Contractual Term [Domain]
Fremont lease agreement.
Fremont Lease Agreement [Member]
Fremont Lease Agreement [Member]
Balance Sheet Location
Balance Sheet Location [Axis]
Balance Sheet Location
Balance Sheet Location [Domain]
Prepaid Expenses and Other Current Assets [Member]
Prepaid Expenses And Other Current Assets [Member]
Other Assets [Member]
Other Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Summary Of Significant Accounting Policies [Line Items]
Foreign currency transaction gain (loss)
Foreign Currency Transaction Gain Loss Before Tax
Income Statement Location
Income Statement Location [Axis]
Income Statement Location
Income Statement Location [Domain]
Research and Development Expense
Research And Development Expense [Member]
Balance at beginning of period
Tax Credit Carryforward Amount
Recognition of credit claims as offset to research and development expense
Income Tax Credits And Adjustments
Receipt of credit claims
Income Tax Reconciliation Tax Credits
Balance at end of period
Research and development tax credit receivable.
Tax incentive receivable
Research And Development Tax Credit Receivable
Tax incentive receivable, current
Tax incentive receivable, long term
Proceeds from lines of credit
Proceeds From Lines Of Credit
Cash collateral associated with corporate credit cards and other leases
Cash Collateral For Borrowed Securities
Cash and cash equivalents
Total cash, cash equivalents and restricted cash shown in the statement of cash flows
Increase (decrease) in escrow deposit.
Escrow deposit
Escrow Deposit
Increase decrease in escrow deposit
Increase Decrease In Escrow Deposit
Sales of strimvelis
Liability associated with the loss contract
Provision For Loss On Contracts
Increase (decrease) in asset acquisition liability, effect of foreign exchange translation.
Asset acquisition liability assumed.
Balance at beginning of period
Asset Acquisition Liability Assumed
Foreign currency translation
Increase Decrease In Asset Acquisition Liability Effect Of Foreign Exchange Translation
Balance at end of period
Asset acquisition liability assumed current.
Asset acquisition liability assumed non current.
Strimvelis loss provision current
Asset Acquisition Liability Assumed Current
Strimvelis loss provision non-current
Asset Acquisition Liability Assumed Non Current
Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table]
Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table]
Award Type
Award Type [Axis]
Award Type
Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain]
Share options
Employee Stock Option [Member]
Unvested Performance-based Restricted Share Units
Restricted Stock Units R S U [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common shares attributable to anti-dilutive shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount
Change in accounting principle, accounting standards update, adopted
Change In Accounting Principle Accounting Standards Update Adopted
Change in accounting principle, accounting standards update, adoption date
Change In Accounting Principle Accounting Standards Update Adoption Date
Change in accounting principle, accounting standards update, immaterial effect
Change In Accounting Principle Accounting Standards Update Immaterial Effect
New accounting pronouncement or change in accounting principle, description
New Accounting Pronouncement Or Change In Accounting Principle Description
Fair value of financial assets transfers between level 1 to level 2
Fair Value Assets Level1 To Level2 Transfers Amount
Fair value of financial assets transfers between level 2 to level 1
Fair Value Assets Level2 To Level1 Transfers Amount
Cash equivalents.
Assets Fair Value Disclosure [Abstract]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table]
Asset Class
Fair Value By Asset Class [Axis]
Asset Class
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation By Asset Class [Domain]
Money Market Funds
Money Market Funds [Member]
Corporate Bonds
Corporate Debt Securities [Member]
Commercial Paper
Commercial Paper [Member]
U.S. Government Securities
U S Treasury And Government [Member]
Level 3
Fair Value By Fair Value Hierarchy Level [Axis]
Fair Value Hierarchy and NAV
Fair Value Measurements Fair Value Hierarchy [Domain]
Level 1
Fair Value Inputs Level1 [Member]
Level 2
Fair Value Inputs Level2 [Member]
Level 3
Fair Value Inputs Level3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents
Cash Equivalents [Abstract]
Total cash equivalents
Cash And Cash Equivalents Fair Value Disclosure
Marketable securities
Marketable Securities [Abstract]
Total marketable securities
Marketable Securities Fair Value Disclosure
Total
Assets Fair Value Disclosure
Amortized Cost
Available For Sale Debt Securities Amortized Cost Basis
Gross Unrealized Gains
Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax
Gross Unrealized Losses
Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax
Credit Losses
Debt Securities Available For Sale Allowance For Credit Loss
Fair Value
Available For Sale Securities Debt Securities
Available for sale securities debt maturities after one through three years amortized cost.
Due in one year
Available For Sale Securities Debt Maturities Remainder Of Fiscal Year Amortized Cost Basis
Due after one year through three years
Available For Sale Securities Debt Maturities After One Through Three Years Amortized Cost
Total
Available For Sale Securities Debt Maturities Single Maturity Date Amortized Cost Basis
Prepaid external research and development expenses.
Construction deposits, current.
Prepaid external research and development expenses
Prepaid External Research And Development Expenses
Inventories
Inventory Net
Other prepayments
Other Prepaid Expense Current
VAT receivable
Value Added Tax Receivable Current
Construction deposit - current
Construction Deposits Current
Non-trade receivables
Nontrade Receivables Current
Total prepaid expenses and other current assets
Schedule Of Property Plant And Equipment [Table]
Schedule Of Property Plant And Equipment [Table]
Long-Lived Tangible Asset
Property Plant And Equipment By Type [Axis]
Long-Lived Tangible Asset
Property Plant And Equipment Type [Domain]
Lab equipment member.
Lab Equipment
Lab Equipment [Member]
Leasehold Improvements
Leasehold Improvements [Member]
Furniture and Fixtures
Furniture And Fixtures [Member]
Office and Computer Equipment
Office Equipment [Member]
Construction-In-Process
Construction In Progress [Member]
Property Plant And Equipment [Line Items]
Property Plant And Equipment [Line Items]
Property and equipment
Property Plant And Equipment Gross
Less: accumulated depreciation
Accumulated Depreciation Depletion And Amortization Property Plant And Equipment
Property and equipment, net
Impairment of construction in process.
Impairment of laboratory equipment.
Depreciation expense
Depreciation
Impairment charges related to construction-in-process
Impairment Of Construction In Process
Impairment charges related to laboratory equipment
Impairment Of Laboratory Equipment
Schedule Of Finite Lived Intangible Assets [Table]
Schedule Of Finite Lived Intangible Assets [Table]
Finite-Lived Intangible Assets by Major Class
Finite Lived Intangible Assets By Major Class [Axis]
Finite-Lived Intangible Assets, Major Class Name
Finite Lived Intangible Assets Major Class Name [Domain]
License Milestones
License [Member]
Finite Lived Intangible Assets [Line Items]
Finite Lived Intangible Assets [Line Items]
Intangible Assets, Cost
Finite Lived Intangible Assets Gross
Intangible Assets, Accumulated Amortized
Finite Lived Intangible Assets Accumulated Amortization
Intangible Assets, Net
Finite Lived Intangible Assets Net
Selling, General and Administrative Expenses
Selling General And Administrative Expenses [Member]
Intangible asset, useful life
Finite Lived Intangible Asset Useful Life
Amortization of intangible assets
2021 (October - December)
Finite Lived Intangible Assets Amortization Expense Remainder Of Fiscal Year
2022
Finite Lived Intangible Assets Amortization Expense Next Twelve Months
2023
Finite Lived Intangible Assets Amortization Expense Year Two
2024
Finite Lived Intangible Assets Amortization Expense Year Three
2025
Finite Lived Intangible Assets Amortization Expense Year Four
Thereafter
Finite Lived Intangible Assets Amortization Expense After Year Four
Other non-current assets.
Construction deposits long-term.
Deferred tax assets
Deferred Tax Assets Liabilities Net
Deposits
Deposits Assets Noncurrent
Deferring financing costs
Deferred Finance Costs Noncurrent Net
Other non-current assets
Other Non Current Assets
Construction deposits - long-term
Construction Deposits Long Term
Total other assets
Accrued external research and development expenses current.
Accrued milestone payments current.
Accrued external research and development expenses
Accrued External Research And Development Expenses Current
Accrued payroll and related expenses, including severance
Employee Related Liabilities Current
Accrued professional fees
Accrued Professional Fees Current
Accrued other
Other Accrued Liabilities Current
Accrued milestone payments
Accrued Milestone Payments Current
Total accrued expenses and other liabilities
Debt Instrument [Table]
Debt Instrument [Table]
Debt Instrument
Debt Instrument [Axis]
Debt Instrument, Name
Debt Instrument Name [Domain]
Term loans available in the first tranche.
Initial Term Loan
The First Tranche Term Loan [Member]
Term loans available in the second tranch.
Second Tranche (Term Loan Available from July 1, 2022 to July 1, 2023)
The Second Tranche Term Loan [Member]
Term loans available in the third tranch.
Third Tranche (Term Loan Available from July 1, 2023 to July 1, 2024)
The Third Tranche Term Loan [Member]
Statistical Measurement
Range [Axis]
Statistical Measurement
Range [Member]
Maximum
Maximum [Member]
Minimum
Minimum [Member]
Variable Rate
Variable Rate [Axis]
Variable Rate
Variable Rate [Domain]
London interbank offered rate floor.
LIBOR
London Interbank Offered Rate Floor [Member]
Debt Instrument, Redemption, Period
Debt Instrument Redemption Period [Axis]
Debt Instrument, Redemption, Period
Debt Instrument Redemption Period [Domain]
Second Tranche (Term Loan Available from July 1, 2022 to July 1, 2023)
Debt Instrument Redemption Period Two [Member]
Third Tranche (Term Loan Available from July 1, 2023 to July 1, 2024)
Debt Instrument Redemption Period Three [Member]
Long-term Debt, Type
Longterm Debt Type [Axis]
Long-term Debt, Type
Longterm Debt Type [Domain]
Term loan.
Term Loan
Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument [Line Items]
Line of credit facility agreement date
Line Of Credit Facility Initiation Date1
Credit facility maximum borrowings
Line Of Credit Facility Maximum Borrowing Capacity
Credit facility, remaining borrowings
Line Of Credit Facility Remaining Borrowing Capacity
Cash and cash equivalent investments
Investments And Cash
Line of Credit Facility, Covenant Terms
Line Of Credit Facility Covenant Terms
Line of credit facility interest payments term.
Line of credit facility straight-line amortization term.
Line of credit facility percentage of final payment.
Debt instrument, annual interest rate
Debt Instrument Basis Spread On Variable Rate1
Line of credit facility interest payments term
Line Of Credit Facility Interest Payments Term
Line of credit facility amortization term
Line Of Credit Facility Amortization Term
Line of credit facility, frequency of payments
Line Of Credit Facility Frequency Of Payments
Line of credit facility, percentage of final payment
Line Of Credit Facility Percentage Of Final Payment
Final payment amount
Line Of Credit Facility Periodic Payment Interest
Repayment of line of credit
Repayments Of Lines Of Credit
Line of credit facility covenants minimum cash allowed.
Line of credit facility minimum cash financial covenant
Line Of Credit Facility Covenants Minimum Cash Allowed
Line of credit facility covenants description
Debt Instrument Covenant Description
Long term debt before accretion issuance costs net.
Long term debt before accretion issuance costs net current.
Long term debt before accretion issuance costs net noncurrent.
Accretion related to final payment.
Long Term Notes And Loans [Abstract]
Notes payable, net of issuance costs
Long Term Debt Before Accretion Issuance Costs Net
Less: current portion
Long Term Debt Before Accretion Issuance Costs Net Current
Notes payable, net of current portion
Long Term Debt Before Accretion Issuance Costs Net Noncurrent
Accretion related to final payment
Accretion Related To Final Payment
Notes payable, long term
Long Term Debt Noncurrent
Long Term Debt By Maturity [Abstract]
2021 (October - December)
Long Term Debt Maturities Repayments Of Principal Remainder Of Fiscal Year
2022
Long Term Debt Maturities Repayments Of Principal In Next Twelve Months
2023
Long Term Debt Maturities Repayments Of Principal In Year Two
2024
Long Term Debt Maturities Repayments Of Principal In Year Three
2025
Long Term Debt Maturities Repayments Of Principal In Year Four
Thereafter
Long Term Debt Maturities Repayments Of Principal After Year Four
Total
Debt Instrument Carrying Amount
Less current portion
Long Term Debt Current
Less unamortized portion of final payment
Unamortized Portion Of Final Payment
Less unamortized debt issuance costs
Unamortized Debt Issuance Expense
Notes payable, long term
Debt instrument, interest expense
Interest Expense Debt
Debt instrument, effective annual interest rate
Debt Instrument Interest Rate During Period
Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]
Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]
Plan Name
Plan Name [Axis]
Plan Name
Plan Name [Domain]
2018 Share Option And Incentive Plan.
2018 Plan
Two Thousand And Eighteen Share Option And Incentive Plan [Member]
2018 Employee Share Purchase Plan.
2018 ESPP
Two Thousand And Eighteen Employee Share Purchase Plan [Member]
2020 Inducement Equity Plan.
Inducement Plan
Two Thousand And Twenty Inducement Equity Plan [Member]
Performance-based Restricted Share Units ("RSUs")
Performance Shares [Member]
Performance-based Restricted Share Units ("RSUs")
Title of Individual
Title Of Individual [Axis]
Title of Individual
Title Of Individual With Relationship To Entity [Domain]
Chief Executive Officer
Chief Executive Officer [Member]
Vesting
Vesting [Axis]
Vesting
Vesting [Domain]
Achievement of At Least Three of Four Milestones
Share Based Compensation Award Tranche One [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Remaining shares available for issuance
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant
Number of Options, Outstanding at December 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number
Number of Options, Granted
Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross
Number of Options, Exercised
Number of Options, Forfeited
Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period
Number of Options, Outstanding at June 30, 2021
Number of Options, Vested and expected to vest, as of June 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Number
Number of Options, Exercisable, June 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number
Weighted Average Exercise Price, Outstanding at December 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price
Weighted Average Exercise Price, Granted
Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price
Weighted Average Exercise Price, Exercised
Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price
Weighted Average Exercise Price, Forfeited
Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding at June 30, 2021
Weighted Average Exercise Price, Vested and expected to vest, as of June 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Outstanding Weighted Average Exercise Price
Weighted Average Exercise Price, Exercisable, June 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price
Weighted-average grant date fair value of share options granted
Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value
Number of shares granted
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period
Vesting rights
Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Rights
Time-based restricted share units.
Time-based RSUs
Time Based Restricted Share Units [Member]
RSUs, Unvested and outstanding at December 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number
RSUs, Granted
RSUs, Vested
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period
RSUs, Forfeited
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period
RSUs, Unvested and outstanding at June 30, 2021
Weighted Average Grant Date Fair Value, Unvested and outstanding at December 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Granted
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Vested
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Forfeited
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Unvested and outstanding at June 30, 2021
Maximum aggregate total fair value of outstanding RSUs
Sharebased Compensation Arrangement By Sharebased Payment Award Equity Instruments Other Than Options Aggregate Intrinsic Value Nonvested
Compensation cost recognized
Allocated Share Based Compensation Expense
Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table]
Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table]
Research and Development
General and Administrative
General And Administrative Expense [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total share-based compensation
Total unrecognized compensation cost of stock option
Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Stock Options
Compensation cost expected to be recognized weighted average period
Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1
Total unrecognized compensation cost
Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Share Based Awards Other Than Options
Schedule Of Restructuring And Related Costs [Table]
Schedule Of Restructuring And Related Costs [Table]
Restructuring Plan
Restructuring Plan [Axis]
Restructuring Plan
Restructuring Plan [Domain]
Menlo park, California.
Menlo Park, California
Menlo Park California [Member]
Fremont, California.
Fremont, California
Fremont California [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring Cost And Reserve [Line Items]
Number of positions eliminated, percent
Restructuring And Related Cost Number Of Positions Eliminated Period Percent
Balance at beginning of period
Restructuring Reserve
Charged to expense
Restructuring Charges
Payments made
Payments For Restructuring
Balance at end of period
Restructuring charges
Employee termination benefits
Severance Costs1
Operating lease right-of-use asset
Operating Lease Impairment Loss
Construction-in-process
Laboratory equipment, Asset write-downs
Charge taken to research and development expense
Construction-in-process, impairment charges
Undiscounted cash flow estimate
Lessee Operating Lease Liability Undiscounted Excess Amount
Discount rate
Lessee Operating Lease Discount Rate
Operating Lease Right Of Use Asset Fair Value
Fair value of ROU asset
Operating Lease Right Of Use Asset Fair Value
Right of use asset, impairment charge
Number of additional programs in preclinical development.
Number of late-stage clinical gene therapy programs.
Number of earlier stage clinical gene therapy program.
Number of additional earlier-stage development programs.
Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table]
Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table]
GSK Asset Purchase And License Agreement.
GSK Asset Purchase and License Agreement
G S K Asset Purchase And License Agreement [Member]
Telethon-OSR license agreements.
Telethon-OSR License Agreements
Telethon O S R License Agreements [Member]
Oxford BioMedica license development and supply agreement.
Oxford BioMedica License, Development and Supply Agreement
Oxford Bio Medica License Development And Supply Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of additional programs in preclinical development
Number Of Additional Programs In Preclinical Development
Number of late-stage clinical gene therapy programs
Number Of Late Stage Clinical Gene Therapy Programs
Number of earlier stage clinical gene therapy program
Number Of Earlier Stage Clinical Gene Therapy Program
Number of additional earlier-stage development programs
Number Of Additional Earlier Stage Development Programs
Total consideration
Asset Acquisition Consideration Transferred
Payment of tiered royalty, maximum percentage.
Milestone payments payable upon achievement of certain sales milestones.
Payment of tiered royalty, maximum percentage
Payment Of Tiered Royalty Maximum Percentage
Milestone payments payable upon achievement of certain sales milestones
Milestone Payments Payable Upon Achievement Of Certain Sales Milestones
Upfront and milestone payments.
In-process research and development expense for upfront and milestone payments.
Upfront payment Description
Upfront payment description
Upfront Payment Description
Upfront and milestone payments
Upfront And Milestone Payments
In-process research and development expense for upfront and milestone payments
In Process Research And Development Expense For Upfront And Milestone Payments
Milestone payment.
Milestone payment
Milestone Payment
Milestone payments receivable.
Strategic collaboration agreement with pharming.
Strategic Collaboration Agreement with Pharming
Strategic Collaboration Agreement With Pharming [Member]
Share purchase agreement with pharming.
Share Purchase Agreement with Pharming
Share Purchase Agreement With Pharming [Member]
Pharming agreements.
Pharming Agreements
Pharming Agreements [Member]
Collaborative Arrangement
Collaborative Arrangement [Member]
Accounts Receivable
Accounts Receivable [Member]
Cash upfront payment received
Proceeds From Collaborators
Milestone payments receivable
Milestone Payments Receivable
Proceeds from premium shares issued..
Total consideration
Issuance of ordinary shares
Common stock consideration
Proceeds From Issuance Of Common Stock
Premium consideration
Proceeds From Premium Shares Issued
Proceeds from upfront payment.
Proceeds from upfront payments attributed to equity sold.
Proceeds from upfront payments attributed to research activities.
Excess proceeds from fair value of shares issued allocated to collaboration agreement.
Total upfront payments
Proceeds From Upfront Payment
Upfront payments attributed to equity sold
Proceeds From Upfront Payments Attributed To Equity Sold
Upfront payments attributed to research activities
Proceeds From Upfront Payments Attributed To Research Activities
Excess proceeds from fair value of shares issued allocated to collaboration agreement
Excess Proceeds From Fair Value Of Shares Issued Allocated To Collaboration Agreement
Proceeds from non-refundable upfront payment.
Non-refundable up-front payment
Proceeds From Non Refundable Upfront Payment
Reimbursement revenue.
Reimbursement Revenue
Reimbursement Revenue [Member]
Upfront and milestone payment revenue.
Upfront and Milestone Payment Revenue
Upfront And Milestone Payment Revenue [Member]
Accounts receivable
Contract With Customer Asset Net Current
Contract liabilities
Contract With Customer Liability Noncurrent
Income tax expense (benefit)
Manufacturing commitments amount due in remainder of fiscal year.
Manufacturing commitments amount due in next twelve months.
Manufacturing commitments amount due in year two.
Manufacturing commitments amount Due In year three.
Manufacturing commitments amount due in year four.
Manufacturing commitments.
Other Commitments [Table]
Other Commitments [Table]
Exclusive Transduction Suites
Supply Commitment [Axis]
Supply Commitment Arrangement
Supply Commitment Arrangement [Member]
Product manufacturing commitments.
Product Manufacturing Commitments
Product Manufacturing Commitments [Member]
Dedicated manufacturing and development resources.
Dedicated Manufacturing And Development Resources
Dedicated Manufacturing And Development Resources [Member]
Exclusive transduction suites.
Exclusive Transduction Suites
Exclusive Transduction Suites [Member]
Other Commitments [Line Items]
Other Commitments [Line Items]
2021 (October - December)
Manufacturing Commitments Amount Due In Remainder Of Fiscal Year
2022
Manufacturing Commitments Amount Due In Next Twelve Months
2023
Manufacturing Commitments Amount Due In Year Two
2024
Manufacturing Commitments Amount Due In Year Three
2025
Manufacturing Commitments Amount Due In Year Four
Total commitment
Manufacturing Commitments
Exchange rate, Euro to U.S. Dollar
Foreign Currency Exchange Rate Translation1
Maximum annual contribution employer matches per employee, percent
Defined Contribution Plan Employer Matching Contribution Percent
Contribution expenses
Defined Contribution Plan Cost Recognized
Accrued expenses related party current.
Schedule Of Related Party Transactions By Related Party [Table]
Schedule Of Related Party Transactions By Related Party [Table]
Related Party
Related Party Transactions By Related Party [Axis]
Related Party
Related Party [Domain]
GSK
GSK
G S K [Member]
Related Party Transaction [Line Items]
Related Party Transaction [Line Items]
Due to related party transactions, accounts payable
Accounts Payable Related Parties Current
Due to related party transactions, accrued expenses
Accrued Expenses Related Party Current
Related party transaction expense
Related Party Transaction Expenses From Transactions With Related Party
Payments on accounts payable
Increase Decrease In Accounts Payable