Summary of Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying unaudited interim consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASUs”) promulgated by the Financial Accounting Standards Board (“FASB”). In the opinion of management, the accompanying unaudited interim consolidated financial statements include all normal and recurring adjustments (which consist primarily of accruals, estimates and assumptions that impact the financial statements) considered necessary to present fairly: •the Company’s financial position as of March 31, 2023 and as of December 31, 2022; and •the Company’s results of operations and cash flows for the three months ended March 31, 2023 and March 31, 2022. Operating results for the Company for the three months ended March 31, 2023 are not necessarily indicative of the results that may be expected for the full year. The unaudited interim consolidated financial statements presented herein do not contain all of the required disclosures under U.S. GAAP for annual financial statements. Notes to the financial statements which would substantially duplicate the disclosure contained in the audited financial statements for fiscal 2022 as reported in the 2022 Annual Report have been omitted. Therefore, these unaudited interim consolidated financial statements should be read in conjunction with the annual audited consolidated and combined financial statements and related notes for Centessa Pharmaceuticals plc found in the Form 10-K filed with the SEC. The Company’s unaudited interim consolidated financial statements include the accounts of Centessa Pharmaceuticals plc, and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less when purchased to be cash equivalents. Cash and cash equivalents include cash in readily available checking accounts, certificate of deposits, money market funds and U.S. Treasury securities.
Short Term Investments	Short Term Investments The Company invests its excess cash in cash deposits, U.S. Treasury securities and SEC-registered money market funds. Securities with original maturities of three months or less when purchased are included in Cash and cash equivalents. The Company considers investments with original maturities greater than three months and remaining maturities less than one year to be short-term investments. As of March 31, 2023, all investments in U.S. Treasury securities were classified as available-for-sale securities, which are recorded at fair value. Unrealized holding gains and losses on available-for-sale securities are reported net of related income taxes in accumulated other comprehensive income until realized. Purchase premiums and discounts are amortized to interest income over the terms of the related securities.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents and short-term investments. The Company’s cash, cash equivalents and short-term investments are held by financial institutions primarily in the United States and the United Kingdom. Amounts on deposit may at times exceed federally insured limits. Management believes that the financial institutions are financially sound, and accordingly, the Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships.
Reclassifications	Reclassifications Certain amounts in the prior period financial statements have been reclassified to conform to the presentation of the current period financial statements. These reclassifications had no effect on previously reported net loss or comprehensive loss.
Use of Estimates	Use of Estimates The preparation of unaudited interim financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the unaudited interim consolidated financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates. Estimates and assumptions are periodically reviewed and the effects of revisions are reflected in the unaudited interim consolidated financial statements in the period they are determined to be necessary. Significant areas that require management’s estimates include share-based compensation assumptions, note purchase agreement assumptions, and accrued research and development expenses.
Property and Equipment, net and Capitalized Software under Cloud Computing Arrangements	Property and Equipment, net and Capitalized Software under Cloud Computing ArrangementsProperty and equipment are recorded at cost and are depreciated using the straight-line method over the estimated useful lives of the respective assets. Property and equipment includes computer equipment, furniture and office equipment. The costs of maintenance and repairs are expensed as incurred. Improvements and betterment that add new functionality or extend the useful life of the asset are capitalized. Costs related to the implementation of cloud computing arrangements that are service contracts incurred during the application development stage are capitalized and included in the same line item as a prepayment for corresponding hosting service fees. Capitalized costs are amortized over the shorter of its estimated useful life and the term of the hosting arrangement, including anticipated extensions. Costs incurred during the preliminary project stage and the post-implementation-operation stage are expensed as incurred. Hosting fees associated with hosting as a service arrangement are expensed on a straight line basis over the term of the hosting arrangement.
Leases	Leases In accordance with ASU No. 2016-02, Leases (“ASC 842”), the Company assesses whether an arrangement is a lease, or contains a lease at the inception of the arrangement. When an arrangement contains a lease, the Company categorizes leases with contractual terms longer than twelve months as either operating or finance. Finance leases are generally those leases that allow us to substantially utilize or pay for the entire asset over its estimated life. Assets acquired under finance leases are recorded in “Property and equipment, net.” All other leases are categorized as operating leases. The Company records right-of use ("ROU") assets and lease obligations for its finance and operating leases, which are initially recognized based on the discounted future lease payments over the term of the lease. As the rate implicit in the Company's leases may not be easily determinable, the Company uses its incremental borrowing rate to calculate the present value of the sum of the lease payments. Lease terms may include options to extend or terminate the lease. The Company will include such options in determining the lease term when it is reasonably certain that the Company will exercise such options. Operating and finance lease ROU assets are recognized net of any lease prepayments and incentives. The Company elected the practical expedient to not separate lease and non-lease components and, accordingly, accounts for them as a single lease component. Operating lease expense is recognized on a straight-line basis over the lease term. Finance lease expense is recognized based on the effective-interest method over the lease term. The Company elected not to recognize ROU assets and lease obligations for any short-term leases, which are defined as leases with an initial term of 12 months or less.
Long-Lived Assets	Long-Lived Assets Long-lived assets, comprised of property and equipment and operating lease right-of-use assets, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated undiscounted future cash flows, then an impairment charge is recognized for the amount by which the carrying value of the asset exceeds the estimated fair value of the asset. No impairments of long-lived assets for the three-month periods ended March 31, 2023 and 2022 were recognized by the Company.
Note Purchase Agreement	Note Purchase Agreement In October 2021, the Company entered into a Note Purchase Agreement (the “Note Purchase Agreement”) with Oberland Capital. Under the terms of the Note Purchase Agreement, Oberland Capital will purchase up to $300 million of 6.0 years, interest-only, senior secured notes (the “Notes”) from the Company including $75 million, funded on October 4, 2021, $125 million available through 2023 at the Company’s option, and $100 million available to fund Mergers and Acquisitions (“M&A”), in-licensing, or other strategic transactions, at the option of the Company and Oberland Capital. In addition to interest payments on the principal, the Company is obligated to pay a milestone payment upon the Company’s first product to obtain regulatory approval and was obligated to pay revenue participation payments, starting on the date of the first commercial sale of lixivaptan. Since the Company’s discontinuation of the development of lixivaptan for the treatment of ADPKD, the revenue participation payment is no longer achievable. The Company evaluated the Notes and determined that the Notes include embedded derivatives that would otherwise require bifurcation as derivative liabilities. Neither the debt instrument nor any embedded features are required to be classified as equity. Therefore, the hybrid financial instrument comprised of the debt host and the embedded derivative liability may be accounted for under the fair value option. The Company elected to carry the Notes at fair value, and the debt instrument is outside the scope of ASC 480, Distinguishing Liabilities from Equity, and thus will be classified as a liability under ASC 470, Debt, in the Company’s financial statements. As the Company has elected to account for the Notes under the fair value option, debt issuance costs were immediately expensed. The fair value of the Note Purchase Agreement represents the present value of estimated future payments, including interest, principal as well as estimated payments that are contingent upon the achievement of specified milestones. The fair value of the Notes is based on the cumulative probability of the various estimated payments. The fair value measurement is based on significant Level 3 unobservable inputs such as the probability of achieving the milestones, anticipated timelines, probability and timing of an early redemption of all obligations under the Note Purchase Agreement and the discount rate. Any changes in the fair value of the liability in each reporting period are recognized in the consolidated statement of operations and comprehensive loss until it is settled.
Net Loss Per Ordinary Share	Net Loss Per Ordinary Share Basic loss per ordinary share is computed by dividing net loss by the aggregate weighted-average number of ordinary shares outstanding. Diluted loss per ordinary share includes the effect, if any, from the potential exercise or conversion of securities, such as convertible preferred shares, stock options, unvested restricted ordinary shares and convertible debt which would result in the issuance of incremental ordinary shares. For diluted net loss per ordinary share, the weighted-average number of ordinary shares is the same for basic net loss per ordinary share due to the fact that when a net loss exists, dilutive securities are not included in the calculation as the impact is anti-dilutive.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2023

The accompanying unaudited interim consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable

guidance is meant to refer to GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASUs”) promulgated by the Financial Accounting Standards Board (“FASB”).

In the opinion of management, the accompanying unaudited interim consolidated financial statements include all normal and recurring adjustments (which consist primarily of accruals, estimates and assumptions that impact the financial statements) considered necessary to present fairly:

•the Company’s financial position as of March 31, 2023 and as of December 31, 2022; and

•the Company’s results of operations and cash flows for the three months ended March 31, 2023 and March 31, 2022.

Operating results for the Company for the three months ended March 31, 2023 are not necessarily indicative of the results that may be expected for the full year. The unaudited interim consolidated financial statements presented herein do not contain all of the required disclosures under U.S. GAAP for annual financial statements. Notes to the financial statements which would substantially duplicate the disclosure contained in the audited financial statements for fiscal 2022 as reported in the 2022 Annual Report have been omitted. Therefore, these unaudited interim consolidated financial statements should be read in conjunction with the annual audited consolidated and combined financial statements and related notes for Centessa Pharmaceuticals plc found in the Form 10-K filed with the SEC.

The Company’s unaudited interim consolidated financial statements include the accounts of Centessa Pharmaceuticals plc, and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less when purchased to be cash equivalents. Cash and cash equivalents include cash in readily available checking accounts, certificate of deposits, money market funds and U.S. Treasury securities.

Short Term Investments

The Company invests its excess cash in cash deposits, U.S. Treasury securities and SEC-registered money market funds. Securities with original maturities of three months or less when purchased are included in Cash and cash equivalents. The Company considers investments with original maturities greater than three months and remaining maturities less than one year to be short-term investments.

As of March 31, 2023, all investments in U.S. Treasury securities were classified as available-for-sale securities, which are recorded at fair value. Unrealized holding gains and losses on available-for-sale securities are reported net of related income taxes in accumulated other comprehensive income until realized. Purchase premiums and discounts are amortized to interest income over the terms of the related securities.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents and short-term investments. The Company’s cash, cash equivalents and short-term investments are held by financial institutions primarily in the United States and the United Kingdom. Amounts on deposit may at times exceed federally insured limits. Management believes that the financial institutions are financially sound, and accordingly, the Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships.

Reclassifications

Certain amounts in the prior period financial statements have been reclassified to conform to the presentation of the current period financial statements. These reclassifications had no effect on previously reported net loss or comprehensive loss.

Use of Estimates

The preparation of unaudited interim financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the unaudited interim consolidated financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates.

Estimates and assumptions are periodically reviewed and the effects of revisions are reflected in the unaudited interim consolidated financial statements in the period they are determined to be necessary. Significant areas that require management’s estimates include share-based compensation assumptions, note purchase agreement assumptions, and accrued research and development expenses.

Property and Equipment, net and Capitalized Software under Cloud Computing Arrangements

Property and Equipment, net and Capitalized Software under Cloud Computing ArrangementsProperty and equipment are recorded at cost and are depreciated using the straight-line method over the estimated useful lives of the respective assets. Property and equipment includes computer equipment, furniture and office equipment. The costs of maintenance and repairs are expensed as incurred. Improvements and betterment that add new functionality or extend the useful life of the asset are capitalized. Costs related to the implementation of cloud computing arrangements that are service contracts incurred during the application development stage are capitalized and included in the same line item as a prepayment for corresponding hosting service fees. Capitalized costs are amortized over the shorter of its estimated useful life and the term of the hosting arrangement, including anticipated extensions. Costs incurred during the preliminary project stage and the post-implementation-operation stage are expensed as incurred. Hosting fees associated with hosting as a service arrangement are expensed on a straight line basis over the term of the hosting arrangement.

Leases

In accordance with ASU No. 2016-02, Leases (“ASC 842”), the Company assesses whether an arrangement is a lease, or contains a lease at the inception of the arrangement. When an arrangement contains a lease, the Company categorizes leases with contractual terms longer than twelve months as either operating or finance. Finance leases are generally those leases that allow us to substantially utilize or pay for the entire asset over its estimated life. Assets acquired under finance leases are recorded in “Property and equipment, net.” All other leases are categorized as operating leases.

The Company records right-of use ("ROU") assets and lease obligations for its finance and operating leases, which are initially recognized based on the discounted future lease payments over the term of the lease. As the rate implicit in the Company's leases may not be easily determinable, the Company uses its incremental borrowing rate to calculate the present value of the sum of the lease payments. Lease terms may include options to extend or terminate the lease. The Company will include such options in determining the lease term when it is reasonably certain that the Company will exercise such options. Operating and finance lease ROU assets are recognized net of any lease prepayments and incentives. The Company elected the practical expedient to not separate lease and non-lease components and, accordingly, accounts for them as a single lease component. Operating lease expense is recognized on a straight-line basis over the lease term. Finance lease expense is recognized based on the effective-interest method over the lease term. The Company elected not to recognize ROU assets and lease obligations for any short-term leases, which are defined as leases with an initial term of 12 months or less.

Long-Lived Assets

Long-lived assets, comprised of property and equipment and operating lease right-of-use assets, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated undiscounted future cash flows, then an impairment charge is recognized for the amount by which the carrying value of the asset exceeds the estimated fair value of the asset. No impairments of long-lived assets for the three-month periods ended March 31, 2023 and 2022 were recognized by the Company.

Note Purchase Agreement

In October 2021, the Company entered into a Note Purchase Agreement (the “Note Purchase Agreement”) with Oberland Capital. Under the terms of the Note Purchase Agreement, Oberland Capital will purchase up to $300 million of 6.0 years, interest-only, senior secured notes (the “Notes”) from the Company including $75 million, funded on October 4, 2021, $125 million available through 2023 at the Company’s option, and $100 million available to fund Mergers and Acquisitions (“M&A”), in-licensing, or other strategic transactions, at the option of the Company and Oberland Capital. In addition to interest payments on the principal, the Company is obligated to pay a milestone payment upon the Company’s first product to obtain regulatory approval and was obligated to pay revenue participation payments, starting on the date of the first commercial sale of lixivaptan. Since the Company’s discontinuation of the development of lixivaptan for the treatment of ADPKD, the revenue participation payment is no longer achievable.

The Company evaluated the Notes and determined that the Notes include embedded derivatives that would otherwise require bifurcation as derivative liabilities. Neither the debt instrument nor any embedded features are required to be classified as equity. Therefore, the hybrid financial instrument comprised of the debt host and the embedded derivative liability may be accounted for under the fair value option. The Company elected to carry the Notes at fair value, and the debt instrument is outside the scope of ASC 480, Distinguishing Liabilities from Equity, and thus will be classified as a liability under ASC 470, Debt, in the Company’s financial statements. As the Company has elected to account for the Notes under the fair value option, debt issuance costs were immediately expensed.

The fair value of the Note Purchase Agreement represents the present value of estimated future payments, including interest, principal as well as estimated payments that are contingent upon the achievement of specified milestones. The fair value of the Notes is based on the cumulative probability of the various estimated payments. The fair value measurement is based on significant Level 3 unobservable inputs such as the probability of achieving the milestones, anticipated timelines,

probability and timing of an early redemption of all obligations under the Note Purchase Agreement and the discount rate. Any changes in the fair value of the liability in each reporting period are recognized in the consolidated statement of operations and comprehensive loss until it is settled.

Net Loss Per Ordinary Share

Basic loss per ordinary share is computed by dividing net loss by the aggregate weighted-average number of ordinary shares outstanding. Diluted loss per ordinary share includes the effect, if any, from the potential exercise or conversion of securities, such as convertible preferred shares, stock options, unvested restricted ordinary shares and convertible debt which would result in the issuance of incremental ordinary shares. For diluted net loss per ordinary share, the weighted-average number of ordinary shares is the same for basic net loss per ordinary share due to the fact that when a net loss exists, dilutive securities are not included in the calculation as the impact is anti-dilutive.