Achilles Therapeutics AI-Powered Precision Cell Therapy Targeting All Tumor Cells March 2023 Non-Confidential © Achilles Therapeutics plc 2023 Forward-Looking Statements / Disclaimers This presentation contains “forward-looking statements,” including statements regarding the proposed development plans and timelines for the Company’s product candidates and the success, cost and timing of its research activities and clinical trials. Forward-looking statements can generally be identified by the use of words su ...

Company Status and Compliance - The company qualifies as an emerging growth company and may take advantage of specified reduced disclosure requirements until it ceases to be one, which could occur when total annual gross revenues reach $1.235 billion or more [329]. - The company is exempt from certain provisions of the Exchange Act applicable to U.S. domestic public companies, including the requirement to file quarterly reports on Form 10-Q [330]. - The company may lose its foreign private issuer status if more than 50% of its securities are held by U.S. residents or if more than 50% of its executive committee or board members are U.S. residents [336]. - Operating as a U.S. listed company incurs significant legal, accounting, and compliance costs that were not present as a private company [339]. - The company may incur significant costs related to compliance with the Sarbanes-Oxley Act and other regulations, which could impact its financial performance [339]. - The company is required to document and evaluate its internal controls over financial reporting, which is both costly and challenging [342]. - The company is refining its disclosure controls and procedures to ensure compliance with reporting requirements under the Exchange Act [411]. Financial Performance and Results - The company reported significant fluctuations in quarterly and annual operating results, making future predictions challenging [376]. - Revenue may depend on development funding and achievement of milestones under collaboration agreements, leading to variability in financial performance [377]. - The company recorded a net loss of $71.2 million for the year ended December 31, 2022, compared to a net loss of $61.1 million in 2021, reflecting an increase of $10.1 million [685]. - Other income increased by $4.2 million to $7.3 million for the year ended December 31, 2022, driven by higher interest income and foreign exchange gains [693]. - The company has not generated any revenue from product sales and does not expect to do so for several years [705]. - Net cash used in operating activities was $59.5 million for the year ended December 31, 2022, compared to $59.3 million in 2021, reflecting a slight increase of 0.3% [710][711]. - The company expects to fund operating expenses and capital expenditures into mid-2025 based on current cash and cash equivalents [717]. Taxation and Financial Obligations - As of December 31, 2022, the company had cumulative United Kingdom carryforward tax losses of $140.5 million, which are expected to be eligible for carry forward and utilization against future operating profits [400]. - The company has historically benefited from the UK R&D tax relief programs, with the SME Program currently allowing a cash rebate of up to 33.35% of qualifying R&D expenditures, which is expected to reduce to up to 18.6% from April 2023 [401]. - The UK Government has announced an increase to the rate of the RDEC credit from 13% to 20% from April 2023, although the RDEC Program is less advantageous than the SME Program [401]. - The company is subject to corporate taxation in both the United States and the United Kingdom, which could be materially affected by changes in tax laws and regulations [406]. - The company faces risks related to potential disagreements with tax authorities, which could result in increased tax liabilities [408]. - The company has accumulated tax losses that can be carried forward indefinitely, subject to certain restrictions, with an annual offset limit of £5.0 million plus 50% of UK taxable profits [681]. Risks and Challenges - The company faces risks from unstable global economic conditions and geopolitical events, which could adversely affect business operations and financial results [371]. - Cybersecurity threats pose a risk to the company's information systems, potentially leading to data breaches and significant financial and legal exposure [372]. - The company may experience increased costs and disruptions due to natural disasters and other business interruptions, impacting financial condition [368]. - The company may be at an increased risk of securities class action litigation, particularly due to the volatility in the biotechnology and pharmaceutical sectors [415]. Research and Development - Research and development expenses increased by $15.0 million to $57.3 million for the year ended December 31, 2022, compared to $42.2 million in 2021, primarily due to higher personnel costs and an impairment loss related to a construction project [685][690]. - The company anticipates significant expenses related to product manufacturing and commercialization as it advances its clinical trials [718]. - The company expects changes to the UK SME Program and RDEC Program to negatively impact future R&D tax credit entitlements starting from April 2023 [680]. - The company recorded an impairment loss of $6.7 million related to a mothballed construction project for a GMP modular facility in London [690]. Shareholder Rights and Corporate Governance - Holders of ADSs may not have the same voting rights as holders of ordinary shares and may not receive voting materials in time to exercise their rights [347]. - The deposit agreement for ADSs allows the depositary to close its books at any time, potentially limiting the transfer of ADSs and withdrawal of underlying ordinary shares [352]. - Holders of ADSs may not be entitled to a jury trial regarding claims arising under the deposit agreement, which could affect legal outcomes [353]. - The enforceability of jury trial waivers in the deposit agreement may limit legal recourse for ADS holders, potentially discouraging lawsuits [357]. - The company’s Articles of Association provide that the courts of England and Wales are the exclusive forum for most shareholder complaints [386]. - Shareholders generally have preemptive rights under English law for any issuance of ordinary shares, differing from U.S. law [385]. - The company must appoint a competent independent advisor during takeover offers, and misleading statements must be corrected immediately [384]. Accounting Policies and Estimates - The company does not identify any critical accounting policies used in the preparation of its financial statements for the year ended December 31, 2022 [731]. - The company estimates accrued research and development expenses based on open contracts and purchase orders, adjusting for actual costs as necessary [732]. - Payments under research contracts depend on successful patient enrollment and completion of clinical trial milestones, with estimates adjusted based on actual service performance [735]. - Share-based compensation is measured based on fair value at the grant date, with expenses recognized over the requisite service period [736]. - The fair value of share options is estimated using the Black-Scholes option-pricing model, with inputs including expected term and volatility derived from comparable public companies [740]. - The company recognizes right-of-use assets and lease liabilities at lease commencement based on the present value of minimum lease payments, using incremental borrowing rates [742].

Achilles Therapeutics AI-Powered Precision TIL Therapy April 2022 © Achilles Therapeutics plc 2022 Forward-Looking Statements This presentation contains express or implied forward-looking statements that are based on our management's belief and assumptions and on information currently available to our management. Although we believe that the expectations reflected in these forward-looking statements are reasonable, these statements relate to future events or our future operational or financial performance, ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 * Not for trading, but only in connection with the registration of the American Depositary Shares. Form 20-F ☐ REGISTRATION STATEMENT PURSUANT TO SECTION 12(b) OR (g) OF THE SECURITIES EXCHANGE ACT OF 1934 OR ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 OR ☐ S ...

Summary of Achilles Therapeutics plc Conference Call Company Overview - **Company**: Achilles Therapeutics plc (NASDAQ: ACHL) - **Focus**: Development of precision T cell therapy targeting solid tumors, leveraging tumor evolution research [4][5] Industry Context - **Industry**: Immuno-oncology, specifically focusing on TIL (tumor-infiltrating lymphocyte) therapies for solid tumors [11] Core Points and Arguments 1. **Clinical Trials**: Updates were provided on ongoing Phase 1/2 clinical trials, specifically the CHIRON and THETIS trials, which are exploring the efficacy of cNeT (clonal neoantigen-reactive T cells) therapy [10][11] 2. **Technology Differentiation**: Achilles utilizes a proprietary VELOS manufacturing process that enhances the potency and specificity of TIL therapies by targeting clonal neoantigens unique to each patient's tumor [6][24] 3. **TRACERx Study**: Exclusive access to the TRACERx study, which has collected extensive genomic data from over 780 non-small cell lung cancer patients, is a significant asset for neoantigen prediction [9] 4. **Early Clinical Data**: Initial results from the first eight patients showed that 88% had detectable cNeT reactivity, with 63% achieving stable disease, indicating potential efficacy [13][14] 5. **Safety Profile**: The therapy demonstrated a manageable toxicity profile, with no higher-grade adverse events reported compared to standard therapies [13] 6. **Process Improvements**: Transitioning to VELOS Process 2 is expected to increase the median cNeT dose by 18-fold compared to Process 1, enhancing the therapeutic potential [20][23] 7. **Future Expectations**: Plans to explore higher doses and combination therapies with immune checkpoint inhibitors in upcoming studies [15][17] Important but Overlooked Content 1. **Financial Position**: As of September 30, the company reported a cash balance of $282 million, providing a runway for ongoing trials and manufacturing scale-up [26] 2. **Regulatory Submissions**: The company plans to file an IND for head and neck squamous cell carcinoma and present GMP data at the December ESMO immuno-oncology meeting [25][23] 3. **Patient Access to Tumor Samples**: Challenges exist in accessing post-treatment tumor samples for analysis, which could provide insights into T cell infiltration and efficacy [50][51] Conclusion Achilles Therapeutics is positioned to advance the field of immuno-oncology through its innovative approach to TIL therapy, focusing on clonal neoantigens and leveraging proprietary manufacturing processes. The early clinical data and ongoing trials suggest promising potential for improved patient outcomes in solid tumors.