T-cell redirection as an immunotherapeutic strategy against HER2-positive breast cancer

Irene Rius Ruiz

Joaquín Arribas López

Despite the successes of therapies against HER2-positive breast cancer, the emergence of resistance limits the efficacy of current treatments. In addition, the expression of HER2 in healthy tissue can lead to the appearance of post-treatment side effects, which can lead to serious toxicities. Therefore, there is a need to develop safer and more effective treatments against HER2-positive metastatic breast cancer. In this thesis, we demonstrate that p95HER2, a truncated form of HER2, is a tumor-specific antigen. That is, this protein is not detected in healthy tissue, it is only found in cancerous tissue. In addition, we know that p95HER2 is expressed in approximately 40% of HER2-positive breast patients, and potentially, in other cancers such as gastric, ovarian and even lung. Therefore, the design of therapies directed against this antigen may result in a safe option for a large group of patients who do not have effective therapeutic options today. In fact, in this thesis we also describe two new immune therapeutic strategies directed against p95HER2. First, we have developed the drug p95HER2-TCB, a bispecific antibody that brings T cells, known as defense cells, closer to tumor cells, thus causing the death of the latter. Through different preclinical models, we have been able to demonstrate that this therapy is effective and safe, not only in tumors located in the breast, but also in brain metastases, which do not have an effective treatment today. In addition, we have not detected side effects in healthy tissue, unlike other therapies directed against HER2. In fact, this project has led to the publication of a scientific article in a high impact factor journal, of which I am the first author. Otherwise, these results have represented a robust proof of concept that confirms that the redirection of T cells against p95HER2 can be an effective option without toxicity in metastatic breast patients and opens the door to developing new alternative therapies. In the second part of the thesis, we have also developed the first versions of p95HER2 CAR Ts, which consists of genetically modifying T cells from patients so that they express receptors that detect tumor cells. We have seen that CAR Ts directed against p95HER2 specifically detect and eliminate tumor cells. In fact, we have recently found that they also extend the survival of mice, demonstrating the clinical applicability of this drug against breast cancer. This has led to the registration of a patent, and has contributed to receiving funding of 1,000,000 euros to launch a phase I clinical trial before 2023.

Our current goal is to bring this novel therapy to clinical trials. Showing that p95HER2 CAR Ts are safe in phase I clinical trials would have an impact at mid-term in approximately 200,000 breast cancer cases per year (data from 2018). Furthermore, if gastric, ovarian and additional cancers are included, the number of patients could significantly increase, and thus, the impact of the commercialization. The development of p95HER2 CAR Ts has already been funded with 1,000,000 euros by the call ‘Grupos Coordinados Asociación Española contra el Cáncer 2019’. This prestigious and highly competitive grant will allow us to start a phase I clinical trial by 2023. Moreover, we have obtained additional funding from public and private sources that will support the preclinical development of the drug in good laboratory practices (GLP). In addition, appropriate pharmacokinetics and safety experiments will be performed, together with three validations of the product, in order to achieve the acceptance of the Agencia Española de Medicamentos y Productos Sanitarios (AEMPS) before starting the phase I clinical trial. In summary, we have successfully obtained both the funding and the strategy to bring this therapy to the clinic. If proven safe in phase I clinical trials, its development would continue by validating its efficacy in phase II and phase III trials, followed by the approval of European and American regulatory agencies and ultimately reaching the market. Apart from the product that we are developing, this research has enabled the negotiation of two different licenses. We are actually very close to sign two license agreements that will expand the therapeutic horizon of p95HER2. These licenses agreements could initially generate more than 500,000 euros. In conclusion, in this thesis we have developed two original and novel therapies that will potentially lead to an improvement in cancer care. The first one, a bispecific antibody (p95HER2-TCB), has directly contributed to a change the paradigm in the HER2 field, proving both the safety and efficacy of targeting the p95HER2 protein. The second one, p95HER2 CAR T cells, could represent a viable, safe and efficacious therapeutic option for close to 400,000 cancer patients diagnosed every year with p95HER2-positive disease, including breast, gastric and other tumor types. Considering that current options are toxic and that there is an unmet medical need - which translates into a market opportunity - the impact of this new therapy is predicted to be high, with a relatively short time to application once the safety and efficacy trials are completed.

HER2-positive Breast Cancer; Therapy Resistance; Post-Treatment Side Effects; Serious Toxicities; Safer Treatments; Effective Treatments; HER2-positive Metastatic Breast Cancer; p95HER2; Tumor-Specific Antigen; Cancerous Tissue; Gastric Cancer; Ovarian Cancer; Lung Cancer; Therapeutic Design; Safe Option; p95HER2-TCB; Bispecific Antibody; T Cells; Defense Cells; Tumor Cells; Preclinical Models; Effective Therapy; Safe Therapy; Breast Tumors; Brain Metastases; No Side Effects in Healthy Tissue; Scientific Article; High Impact Factor Journal; Robust Proof of Concept; T Cell Redirection; Toxicity-Free Option; Alternative Therapies; p95HER2 CAR Ts; Genetically Modified T Cells; Tumor Cell Detection; Tumor Cell Elimination; Extend Mouse Survival; Clinical Applicability; Breast Cancer Drug; Patent Registration; Funding; Phase I Clinical Trial.