Adaptimmune Therapeutics (ADAP) Risk Factors

We have no cell therapies approved for commercial sale, have not generated any revenue from sales of our cell therapies, and do not anticipate generating any revenue from sales of our cell therapies until sometime after we receive regulatory approval, if at all, for the commercial sale of a cell therapy. We may never become profitable. Our ability to generate revenue and achieve profitability depends on many factors, including: - progressing our cell therapies through preclinical development and clinical development without substantial delays;- demonstrating a favorable benefit (efficacy parameters): risk (safety) profile for our cell therapies;- obtaining regulatory approvals and marketing authorizations for our cell therapies;- developing sustainable and scalable manufacturing and supply processes for our cell therapies to support commercial supply;- obtaining market acceptance, pricing and reimbursement of our cell therapies as viable treatment options;- the costs of commercializing any cell therapy including any post-marketing approval obligations;- the indications any cell therapy is approved in, the patient population treatable with any cell therapy and the speed with which we are able to launch a cell therapy and commercialize that cell therapy with treatment centers; and

Developing a commercially viable process is a difficult and uncertain task, and there are risks associated with scaling to the level required for advanced clinical trials or commercialization, including, among others, requirements to characterize the manufacturing process, increased costs, potential problems with process scale-out, process reproducibility, stability issues, lot consistency, loss of product, and timely availability of reagents or raw materials or contract manufacturing services or facilities. A failure to develop such a commercially viable process within anticipated timescales may prevent or delay progression of our T-cell therapies into pivotal clinical trials and ultimately commercialization. This failure to develop a timely process may result from, for example, inability to scale-up within required timelines, inability to put in place the required processes and control measures for a commercial process, inability to timely develop systems for automation of the process or failure of third parties (including vector suppliers) to put in place adequate facilities or processes to enable commercial manufacture. In addition, we may ultimately be unable to reduce the expenses associated with our cell therapies to levels that will allow us to achieve a profitable return on investment. Reduction of the costs associated with manufacture requires significant financial investment which may not be available to us.

In 2012, the FDA established a Breakthrough Therapy designation which is intended to expedite the development and review of products that treat serious or life-threatening diseases when "preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development." The designation of a cell therapy as a Breakthrough Therapy provides potential benefits that include more frequent meetings with the FDA to discuss the development plan for the cell therapy and ensure collection of appropriate data needed to support approval; more frequent written correspondence from the FDA about things such as the design of the proposed clinical trials and use of biomarkers; intensive guidance on an efficient drug development program, beginning as early as Phase 1; organizational commitment involving senior managers; and eligibility for rolling review and Priority Review. We have obtained RMAT designation (Regenerative Medicine Advanced Therapy designation) from the FDA for afami-cel for the treatment of synovial sarcoma. We have also obtained RMAT designation for ADP-A2M4CD8 for the treatment of ovarian cancer. We may apply for similar status or accelerated programs in other countries and for other of our products and indications. However, given the novel nature of our cell therapies, it is difficult for us to predict whether the FDA or other regulatory authorities will approve such requests or what further clinical or other data may be required to support an application for such accelerated approval procedures. It is possible that the FDA could rescind our RMAT or other designations, if the agency determines that our cell therapies no longer meet the qualifying criteria. Breakthrough Therapy and RMAT designations do not change the standards for product approval, and products with such designations do not always obtain marketing approval or timely marketing approval. Additionally, other treatments from competing companies may obtain the designations and impact our ability to develop and commercialize our cell therapy, which may adversely impact our business, financial condition or results of operation. We may also seek Accelerated Approval under the FDA's Fast Track And Accelerated Approval programs, the FDA may approve a drug or biologic for a serious or life-threatening illness that provides meaningful therapeutic benefit to patients over existing treatments based upon a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity, or prevalence of the condition and the availability or lack of alternative treatments. For drugs and biologics granted Accelerated Approval such as afami-cel, post-marketing confirmatory trials have been required to describe the anticipated effect on irreversible morbidity or mortality or other clinical benefit. These confirmatory trials must be completed with due diligence. Moreover, the FDA may withdraw approval of our cell therapy or indication approved under the accelerated approval pathway if, for example: - the trial or trials required to verify the predicted clinical benefit of our cell therapy fail to verify such benefit or do not demonstrate sufficient clinical benefit to justify the risks associated with the drug;- other evidence demonstrates that our cell therapy is not shown to be safe or effective under the conditions of use;- we fail to conduct any required post approval trial of our cell therapy with due diligence; or - we disseminate false or misleading promotional materials relating to the relevant cell therapy. The FDA's Accelerated Approval program has come under increased scrutiny in recent years from both internal and external stakeholders have raised concerns that confirmatory trials have not been completed or have not demonstrated intended effect. Recent legislation (FDORA) has increased the FDA's authority to impose more stringent requirements on the timing and conduct of confirmatory trials, and on the FDA's ability to expedite the withdrawal from approval of a biological product when confirmatory trials have not been completed or do not show intended effect. In Europe, the EMA has implemented the so-called Priority Medicines ("PRIME") scheme in order support the development and accelerate the approval of complex innovative medicinal products addressing an unmet medical need. The PRIME status enables early dialogue with the relevant EMA scientific committees and, possibly, some payers; and thus reinforces the EMA's scientific and regulatory support. It also opens accelerated assessment of the marketing authorization application (150 days instead of 210 days). The PRIME scheme, which is decided by the EMA, is reserved for medicinal products that may benefit from accelerated assessment, i.e. medicines of major interest from a public health perspective, in particular from a therapeutic innovation perspective. In 2020, the EMA granted access to the PRIME scheme to afami-cel for the treatment of certain patients with synovial sarcoma. We may apply for PRIME status for other of our cell therapy products. There can be no assurance that any application will be successful in obtaining PRIME status.

Administration of cell therapies is patient-specific. The process requires careful handling of patient-specific products and fail-safe tracking to ensure that the tracking process is without error and that patient samples are tracked from patient removal, through manufacturing and re-administration to the same patient. While such mechanisms are in place, should the tracking process fail, whether at our own facility, a third party facility or at any point in the manufacturing and supply process, a patient could receive another patient's T-cells resulting in significant toxicity and potentially patient fatality. We will need to invest in enhanced systems, such as bar coding, to further ensure fail safe tracking. There is always a risk of a failure in any such system. Inability to develop or adopt an acceptable fail-safe tracking methodology and handling regime may delay or prevent us from receiving regulatory approval and/or result in significant toxicity and potentially patient fatality if a patient receives another patient's T-cells. This risk may be increased where cell therapies are used in clinical programs that we do not control or sponsor and, should an error be made in the administration of our cell therapies in such clinical programs, this could affect the steps required in our own clinical programs and manufacturing process requiring the addition of further tracking mechanisms to ensure fail-safe tracking. The tracking systems required to further ensure safe patient administration may also require increased administration to satisfy other regulatory requirements, for example, data protection requirements in Europe. The need to ensure tracking systems are adequate and to comply with these additional regulatory requirements may result in delay to the start of trials or the need to obtain additional regulatory licenses or consents prior to starting such trials.

We have a platform process which may enable us to treat patient populations with an "off-the-shelf" product. However, our research program may not be successful, might not be carried out within the timescales currently anticipated, or even if successful might not result in a cell therapy that can be used to treat patients or achieve a profitable return on investment. In particular the various cell lines developed during this process will need to be properly characterized and produced in accordance with regulatory requirements and this development process can take a significant amount of time and resource to ensure that any process or cell lines can be used for the production of clinical stage and ultimately commercial stage products. It is not known at this time whether the cell therapy candidates resulting from the process will have a similar profile of activity to our existing cell therapy products or whether such cell therapy candidates will be safe to administer to patients. Delays may occur at any part of the process, including obtaining results during development that necessitate a requirement to repeat or modify steps in the process. The regulatory requirements for an off-the-shelf product are not known and regulators could require significant additional development steps, which in turn could delay our ability to enter clinical development with our off-the-shelf cell therapies.

The success of our cell therapies depends on both the identification of target peptides presented on cancer cells, which can be bound by our cell therapy products, and isolation and affinity enhancement of receptors including TCRs, which can be used to treat patients if regulatory approval is obtained. Any failure to identify and validate further target peptides will reduce the number of potential cell therapies that we can successfully develop, which in turn will reduce the commercial opportunities available to us and increase our reliance on our existing cell therapies. Delays in our ability to identify and develop target peptides and cell therapies, including as caused by lack of financing, COVID-19 or similar pandemics, may also impact our ability to progress development of programs and obtain additional funds to support our business. We may not develop new cell therapy candidates for which the safety and efficacy profiles enable progression to and through preclinical testing and into clinical development. Failure to identify further candidates for progression into preclinical testing and clinical programs will significantly impact our pipeline of cell therapies and also increase our reliance on the cell therapies currently in clinical development. If resources become limited or if we fail to identify suitable target peptides, receptors including TCRs or affinity-enhanced receptors, our ability to submit INDs for further cell therapies may be delayed or never realized, which would have a materially adverse effect on our business.

Our cell therapies and their potential associated risks are still under investigation. Our cell therapies may not work in the way that we currently anticipate and affinity modification of the receptors within T-cells or other cellular therapies may not produce the anticipated enhancements in activity. For example, there is a potential risk that, given that the TCR chains in our T-cells are produced separately and then assembled within patient T-cells into full TCRs, the TCR chains from both transduced and naturally occurring T-cells could be assembled into an unintended end TCR due to mispairing of TCR chains, which could create unknown recognition and cross-reactivity problems within patients. Although this phenomenon has not been reported in humans, it remains a theoretical risk for our cell therapies and other similar cell therapies and is still being studied and investigated. This could delay regulatory approval, if any, for the relevant cell therapy. To the extent that any mispairing is identified, either in our or our competitors' clinical trials, additional investment may be required in order to modify relevant cell therapies and to further assess and validate the risk of such mispairing to patients. Following modification of the relevant cell therapy, such modified cell therapy may not remain suitable for patient treatment and may not eliminate the risk of mispairing of TCR chains and regulatory approval may not be obtained on a timely basis or at all in relation to such modified cell therapy. The occurrence of such events would significantly harm our business, prospects, financial condition and results of operations.

Clinical trials, depending on the stage, can be costly as well as difficult to implement and define, particularly with technologies that are not tried and tested, such as our cell therapies. These factors can lead to a longer clinical development timeline and regulatory approval process, including a requirement to conduct further or more complex clinical trials in order to obtain regulatory approval. Regulatory authorities may disagree with the design of any clinical program, and designing an acceptable program could lead to increased timeframes for obtaining of approvals, if any. In addition, progression of clinical trials depends on the ability to recruit suitable patients to those trials and delay in recruiting will impact the timeframes of such clinical trials and as a result the timeframes for obtaining regulatory approval, if any, for the relevant cell therapy. In particular, eligible patients may need to be screened for the target peptide and HLA type, which may reduce the number of patients who can be recruited for any clinical program. The ability to administer cell therapies to patients in accordance with set protocols for the clinical trials and the results obtained depends on patient participation for the duration of the clinical trial, which many of these patients are unable to do because of their late-stage cancer and limited life expectancy.

Although we have recruited a team that has significant experience with clinical trials, as a company we have limited experience in conducting clinical trials through to regulatory approval. In part because of this lack of experience, we cannot be certain that planned clinical trials will begin or be completed on time, if at all. Large-scale trials would require significant additional financial and management resources, and reliance on third-party clinical investigators, contract research organizations, or CROs, or consultants. Relying on third-party clinical investigators, consultants or CROs may force us to encounter delays that are outside of our control.

There is a risk in any clinical trial that side effects from cell therapies will require a hold on, or termination of, clinical programs or further adjustments to clinical programs in order to progress any cell therapy. Our cell therapy must demonstrate an acceptable benefit/risk profile in its intended patient population and for its intended use. The benefit/risk profile required for product licensure will vary depending on these factors and may include not only the ability to show tumor shrinkage, but also adequate duration of response, a delay in the progression of the disease and/or an improvement in survival. For example, response rates from the use of our cell therapies may not be sufficient to obtain regulatory approval unless we show an adequate duration of response. The regulatory authorities (including the FDA) may issue a hold on our clinical trials as a result of safety information and data obtained in third party clinical trials or in relation to third party products. Any such hold will require addressing by us and will inevitably delay progression of the clinical trials concerned, if such clinical trials progress at all. In addition, even if such trials are successfully completed, the FDA or foreign regulatory authorities may not interpret the results as we do. Accordingly, more trials may be required before we can submit any cell therapy for regulatory approval or additional data may be required in order to obtain full approval. To the extent that the results of the trials are not satisfactory to the FDA or foreign regulatory authorities for support of a marketing authorization application, we may be required to expend significant resources, which may not be available to us, to conduct additional trials and development in support of potential approval of our cell therapies. We cannot predict whether any of our cell therapies will satisfy regulatory requirements at all or for indications in which such cell therapies are currently being evaluated as part of any clinical programs.

Any delay in our clinical trials will impact our ability to obtain clinical data from those trials and our ability to progress our business along anticipated timelines and to raise capital. Delays in clinical trials can also increase the costs incurred in performing those clinical trials or necessitate a need to initiate additional clinical trial sites. Our ability to progress our clinical trials is dependent on a number of factors including: - Finding clinical sites prepared to carry out the relevant clinical trials, screening of patients by the clinical sites, recruitment of patients both in terms of number and type of patients and general performance of the relevant clinical site. - The ability of our clinical sites to recruit patients on the timelines we expect. It can be difficult for clinical sites to find patients that express both the required HLA-type (if required) and required antigen type and which also meet the inclusion criteria for our clinical trials. In addition, during the COVID-19 pandemic, resources at clinical sites are being prioritized towards treatment of COVID-19 and as a result there may be a delay in their ability to progress our clinical trials, recruit and enroll patients into clinical trials or to start new clinical trials. - The patient population in which any required peptide antigen is presented. The patient population may be lower than expected which will increase the timescales required to find and recruit patients into the applicable clinical trial. Screening of a large number of patients is required to identify HLA and tumor antigen positive patients for all of our clinical trials with our engineered T-cells. - Our ability to select, initiate and activate clinical sites on the timelines we expect. Selection and activation of clinical trial sites can take a long period of time and includes requirements to assess the clinical trial site, obtain IRB approval of clinical trial protocols, negotiate and execute clinical trial agreements and educate study staff to enable them to carry out the clinical trial. - Any requirement to change clinical trial design as the clinical trial progresses. It is also difficult to predict whether changes may be required to any clinical trial design as our clinical trials progress. The need to make changes to any clinical trial design can result in delays to the performance of that clinical trial whilst any changes are approved by the FDA or other relevant authority and implemented at applicable clinical trial sites. - Any competition for patients at our clinical sites. Many of our clinical trial sites have multiple clinical trials ongoing which compete for patients in any specific indication. We may have to wait before treating patients while patients complete existing clinical trials or receive other treatment therapies for their cancer. Moreover, because our cell therapies represent a departure from more commonly used methods for cancer treatment, potential patients and their physicians may opt to use conventional therapies, such as chemotherapy and hematopoietic cell transplantation, rather than enrollment in any of our current or future clinical trials. This may also mean we cannot recruit patients at a suitable time in their disease progression. - Any change in the standard of care for patients. Where standard of care for patients changes clinical sites may no longer be prepared to continue with any clinical trial or require amendments to agreed protocols for clinical trials. Such circumstances can lead to the suspension of the relevant clinical trial at a site, inability to recruit further patients at that clinical site or a requirement to amend the protocol, all of which will delay or potentially halt progression of a cell therapy through clinical trials. - Any country-specific requirement. In certain countries, additional data, studies or documentation may be required ahead of any clinical trial starting. For example, comparability studies may be required in relation to any changes in manufacturing process and the extent of these comparability studies can vary between different countries. This can result in delays to the start of any clinical trials in those countries and lead to increased research and development being required ahead of the start of those clinical trials. - The severity of the disease we are trying to treat and the type of patient we are trying to recruit. For many of our clinical trials patients have received numerous prior therapies and have few or no other remaining treatment options. Given the late stage of their disease the patients also tend to be very ill and hence require treatment quickly and have the potential for increased SAEs following treatment. Depending on the protocol it can be difficult to find patients that meet the inclusion requirements for our clinical trials and can wait for manufacture of our cell therapy products. - The clinical trial protocol design and in particular the inclusion and exclusion requirements applicable to the clinical trial. - Patient referral practices. It is common for investigators or physicians not to refer patients to other investigators or physicians either within their own clinical sites or to other clinical sites. This increases the number of clinical sites which have to be initiated in order to recruit patients to our clinical trials. - Availability of reimbursement from insurance companies. The availability of reimbursement for patients to participate in clinical trials can impact on their ability to enroll in our clinical trials. Even if we are able to enroll a sufficient number of patients in our clinical trials, delays in patient enrollment may result in, and have resulted in, increased costs or may affect the timing or outcome of the planned clinical trials, which could prevent completion of these trials and adversely affect our ability to advance the development of our cell therapies. Certain of our clinical trials include dose escalation studies in which the dose of cell therapies administered to patients is varied or initial studies in which the pre-treatment regimen may be varied, for example, a regimen with and without fludarabine. The outcome of such dose escalation or initial studies will inform the clinical study going forward. However, the need to carry out dose escalation or other initial studies may result in delays in data from such clinical programs while the most suitable dose or regimen is assessed. For example, the trial design for our cell therapy trials includes dose escalation and therefore efficacy data may not be obtained from initial patients treated in such studies during the dose escalation phase.

Development of a pharmaceutical or biologic therapy or product has inherent risks based on differences in patient population and responses to therapy and treatment. The mechanism of action and impact on other systems and tissues within the human body following administration of our cell therapies is complex and not completely understood, which means that we cannot predict the long-term effects of treatment with any of our cell therapies (whether by us or a collaborator). In addition, it is not possible for any pre-clinical safety package to completely identify all potential safety risks. For example, there is a risk that the target (or similar) peptide to which any T-cell is directed may be present in both patients' cancer cells and other non-cancer cells and tissues. Cross-reactivity or allo-reactivity (binding to peptides presented on other HLA types) could also occur where the affinity-enhanced engineered TCR contained within any cell therapy including our T-cells binds to peptides presented by HLAs other than the HLA type for which the relevant TCR was developed. Should any of these cross-reactivities occur, patients may suffer a range of side effects associated with the T-cell binding to both the cancer cells and/or other cells and tissues and such side effects could cause patient death. The extent of these side effects will depend on which cells and tissues are affected as well as the degree to which the target (or similar) peptide is expressed in these cells and tissues. Any unacceptable toxicities arising in ongoing clinical programs could result in suspension or termination of those clinical programs. The more serious adverse events ("SAEs") that are reported the greater the risk of suspension of termination of clinical programs, even where the SAEs are unrelated to each other or to our cell therapies. Our patients undergo lymphodepletion prior to receiving our cell therapies which leaves them immuno-compromised for a period of time after the lymphodepletion and increases their risk of contracting other unrelated diseases or pathogens including COVID-19. The treatment regimen used in our protocols, in particular the use of chemotherapy, also carries an inherent risk of cytopenia (including pancytopenia), where blood cell levels reduce to lower than normal. If blood cell levels do not recover sufficiently the patient may suffer serious adverse events, which may even be life threatening. There have been multiple events of pancytopenia as well as SAEs similar to those reported across our clinical trials; these are multifactorial in etiologies and could result in regulatory authorities imposing a hold on one or more clinical programs whilst the events are investigated further. Serious adverse events seen with other immunotherapy products, such as the severe cytokine release syndrome ("CRS") and neurotoxicity events observed with CD19-directed CAR T-cell treatments, may also occur at any stage of the clinical program. Further, following infusion of any of our T-cells, there may be a transient inflammatory reaction of the disease to the treatment. Symptoms in any given subject would be dependent on the location and other characteristics of their tumor. For example, subjects with lung tumors may experience dyspnea. Cardiac toxicities may be observed in patients with pre-existing cardiac or pericardial masses. These inflammatory reactions and related symptoms may be mild and self-limited, but can be severe, potentially life-threatening and require medical intervention. Any side effects may also result in the need to perform additional trials, which will delay regulatory approval for such cell therapies and require additional resources and financial investment to bring the relevant cell therapy to market. Use of cell therapies in combination with other third party products or therapies may increase or exacerbate side effects that have been seen with our cell therapies alone or may result in new side effects that have not previously been identified with our cell therapies alone. Any undesirable side effects seen in combination trials may affect our ability to continue with and obtain regulatory approval for the combination therapy, but may also impact our ability to continue with and obtain regulatory approval for our cell therapies alone. Summary information on adverse events ("AEs") seen in relation to each of our cell therapies are provided below Afami-cel: - As of December 27, 2023, 156 patients received at least one dose of transduced cells of afami-cel across multiple studies.  138 (88.5%) patients experienced adverse events. Adverse events occurring in >10% of subjects considered by investigators to be at least possibly related to afami-cel include CRS, pyrexia, neutropenia/neutrophil count decreased, fatigue, leukopenia/WBC decreased, sinus tachycardia/tachycardia, lymphopenia/ lymphocyte count decreased, nausea, hypotension rash, thrombocytopenia/platelet count decreased, chills, febrile neutropenia, anaemia/RBC decreased, decreased appetite and headache. - Serious adverse event (SAEs), considered by investigators to be at least possibly related to afami-cel were reported for 38 (24.4%) subjects under the program.  These events include empyema, sepsis, cytokine release syndrome, pleural effusion, pneumothorax, pulmonary embolism, pyrexia, anemia, aplastic anemia, pancytopenia, cerebrovascular accident, encephalopathy, neurotoxicity,  arrhythmia, alanine aminotransferase increased, aspartate aminotransferase increased, blood alkaline phosphatase increased, platelet count decreased, lymphoproliferative disorder, deep vein thrombosis, superior vena cava occlusion, acute kidney injury, arthralgia,  pulmonary hemorrhage, adrenal insufficiency, white blood cell count decreased and rash.  Two of these subjects have had treatment related fatal SAEs: one patient experienced pancytopenia/aplastic anemia and the other experienced a cerebrovascular accident (stroke). - Five subjects experienced long term follow up events. The events were thrombocytopenia/Platelet count decreased, sepsis, bacteraemia, Covid-19, hyperthyroidism, and myelodysplastic syndrome. ADP-A2M4CD8: - As of November 22, 2023, in the SURPASS study, there have been 46 patients treated with ADP-A2M4CD8 monotherapy.  The adverse events occurring in >10%  of patients treated with ADP-A2M4CD8 monotherapy (n=46) and considered by investigators to be at least possibly related to ADP-A2M4CD8 include CRS, neutropenia/neutrophil count decreased, fatigue, anemia/red blood cell count decreased, thrombocytopenia/platelet count decreased, immune effector cell-associated neurotoxicity syndrome (ICANS), pleural effusion, pyrexia, rash, dyspnea, hypoxia, leukopenia/ white blood cell count decreased, sinus tachycardia/tachycardia, decreased appetite, febrile neutropenia, and lymphopenia/ lymphocyte count decreased. - SAEs, considered by investigators to be at least possibly related to ADP-A2M4CD8 monotherapy, were reported for 23 (50.0%) patients in the study.  These events include CRS, ICANS, drug reaction with eosinophilia and systemic symptoms (DRESS Syndrome), rash, hypoxia, dyspnea, plueral effusion, device related infection, pneumonia, sepsis, anemia, pancytopenia, pyrexia, myocarditis, small intestinal obstruction, infusion related reaction, blood creatinine increased, tumor lysis syndrome, and myositis. Three of these patients had treatment-related fatal SAEs (pancytopenia, CRS, and myositis).In addition, there have been 10 patients treated with nivolumab in combination with ADP-A2M4CD8. Nine out of 10 subjects had AEs related to T-cell infusion, including CRS, rash, pyrexia, fatigue, C-reactive protein increased, decreased appetite, febrile neutropenia, headache, hypotension, ICANS, infusion related reaction, lymphopenia/lymphocyte count decreased, sinus tachycardia/tachycardia, stomatitis and thrombocytopenia/platelet count decreased. Febrile neutropenia, fatigue, and hypotension were the only AEs related to T-cell infusion and nivolumab. - In the SURPASS-2 study (ADP-0055-002), there have been 3 patients treated with ADP-A2M4CD8 monotherapy. The adverse events considered by investigators to be at least possibly related to ADP-A2M4CD8 include rash, sciatica, CRS, pyrexia and respiratory failure. CRS was the only SAE considered by investigators to be at least possibly related to ADP-A2M4CD8 monotherapy. - Across all ADP-A2M4CD8 trials, 32 total patients treated with ADP-A2M4CD8 monotherapy continue in long term follow up as at date of data cut-off. No related AE/SAEs have been reported. Lete-cel: - As of January 27, 2023, 198 patients out of 199 patients experienced treatment emergent adverse events. Adverse events (AEs) occurring in >10% of subjects considered by investigators to be at least possibly related to Lete-cel include cytokine release syndrome (CRS),neutropenia/neutrophil count decreased, leukopenia/white blood cell decreased, thrombocytopenia/platelet count decreased, anaemia/red blood cell count decreased, pyrexia, rash/rash maculo-papular, fatigue, diarrhea, nausea, febrile neutropenia, hypophosphatemia, alanine aminotransferase increased, tachycardia, dyspnoea, decreased appetite, aspartate aminotransferase increased, lymphopenia/lymphocyte count decreased, hypotension, hypokalaemia, alopecia, chills, hypocalcemia, headache, hyponatremia, hypoalbuminemia, cough, vomiting, hypomagnesaemia, pruritus, blood alkaline phosphatase increased. - Serious adverse event (SAEs), considered by investigators to be at least possibly related to lete-cel, were reported for 92 (46%) subjects under the program.  These events include CRS, febrile neutropenia, neutropenia/neutrophil count decreased, pyrexia, rash/rash maculo-papular, thrombocytopenia/platelet count decreased, anemia/RBC decreased, dyspnea, hypotension, pancytopenia, unspecified GVHD – other (lung, bone marrow, not specified), pleural effusion, acute GVHD –other (lung, bone marrow, not specified), device related infection, diarrhoea, nausea, bacteraemia, blood bilirubin increased , bone marrow failure, cardiac arrest, dermatitis exfoliative generalized,Guillain-Barre syndrome, hemorrhage intracranial, hyponatremia, hypoxia, immune effector cell-associated neurotoxicity syndrome (ICANS), leukopenia/white blood cell decreased, neutropenic sepsis, pericardial effusion, pneumonitis, staphylococcal infection, and tumor pain. - As of January 27, 2023, one hundred and eighty-two patients treated with lete-cel were in long term follow-up (LTFU) phase. In 90 safety population, potential Grade =3 delayed AEs includes pulmonary alveolar hemorrhage, BK virus infection, febrile neutropenia, herpes zoster, Guillain-Barre syndrome, peripheral motor neuropathy, and peripheral sensory neuropathy.

Progression of new cell therapies into clinical trials is inherently risky and dependent on the results obtained in preclinical programs, the results of other clinical programs and any other activities which may impact our ability to commence clinical trials, for example, availability of manufacturing process and components. If any issues are identified during any cell therapy development, we may experience significant delays in development of pipeline candidates including our PRAME and CD70 programs and in existing clinical programs including our SURPASS and SURPASS-3 programs. This may also impact our ability to achieve certain financial milestones and the expected timeframes to market any of our cell therapies. The FDA or other regulatory authorities may not approve any IND (or equivalent application) for any of our future cell therapies, or for new indications for our cell therapies already in clinical trials, or may require amendments to existing protocols (including as a result of the COVID-19 pandemic or other similar pandemics). For example, we amended the protocols for our clinical trials in response to reported serious adverse events ("SAEs") of prolonged serious pancytopenia in our clinical trials. Such amendments and updates may delay our clinical trials, may require changes or resubmission of our INDs, or may result in or be related to a halt in our planned or contemplated clinical trials. We conduct clinical trials at sites in the U.K. and European Union. This requires gaining the approval of country specific review bodies for GMO application and Clinical Trial Application ("CTA"). As this is not a harmonized process, the requirements can vary considerably, and delays can be incurred at a country level. For example, the information required in relation to manufacturing processes or assays may differ between countries and may require additional testing to be conducted in order for approval to be obtained.

The patient response data that has been reported in our SURPASS and SURPASS-3 trials represents data from small numbers of patients within each study at the applicable dosing level. As such, the data is initial data, and there is no assurance that any responses will persist, that we will see responses in any other patients or that such patients will not suffer severe adverse events which may result in a delay or halt to any clinical trial. Further data may be required in order to progress cell therapies to the next stage of development. Negative results in one clinical trial may also impact ability to proceed with development in other clinical trials given the common technology platform and similarity of other aspects of our clinical programs. Like other biologic products, we expect there may be greater variability in results for cell therapies which are administered on a patient-by-patient basis than for "off-the-shelf" products, like many other biologics. There is typically an extremely high rate of attrition from the failure of any products proceeding through clinical trials. Cell therapies in later stages of clinical trials may fail to show the desired safety and efficacy profile despite having progressed through preclinical programs and initial clinical trials. A number of companies in the biopharmaceutical industry have suffered significant setbacks in advanced clinical trials due to lack of efficacy or unacceptable safety issues, notwithstanding promising results in earlier trials. Most biologic candidates that begin clinical trials are never approved by regulatory authorities for commercialization. We may therefore be unsuccessful in demonstrating the required efficacy and safety profile from the performance of any of our clinical programs. We are aware that certain patients do not respond to our cell therapies and that other patients may relapse or cease to present the peptide being targeted by such cell therapies. The percentage of the patient population in which these events may occur is unknown, but the inability of patients to respond and the possibility of relapse may impact our ability to conduct clinical trials, to obtain regulatory approvals, if at all, and to successfully commercialize any cell therapies. We plan to provide further data updates as and when the applicable data is believed to be sufficiently mature.  Given the nature of T-cell therapies and the time taken to observe patient responses to our cell therapies, we cannot provide any assurance that further data updates will be provided frequently or that such data updates will be available at any particular time.

Our cell therapies may not achieve regulatory approval or proceed to the next stage of development. We have filed our first BLA for afami-cel and the FDA is currently reviewing that BLA. We do not know if the FDA will grant approval for afami-cel or whether additional activities, if any, will be required to be performed prior to such approval being granted or after such approval being granted. All of our other cell therapies require further development before a BLA can be filed with any regulatory authority to permit commercialization. Results seen in early clinical trials, for example, with our ADP-A2M4CD8 cell therapy candidate may not be predictive of the data we will obtain in our later phase clinical trials. Negative results in any cell therapy clinical program may also impact our ability to continue with clinical development of other similar cell therapies. Although each cell therapy may target a different cancer peptide or protein, the underlying technology platform and other aspects of our clinical programs are the same or substantially similar for many of our cell therapies. Accordingly, a failure or delay in any one program may affect the ability to obtain regulatory approval to continue or conduct clinical programs for other cell therapies.