CLDN6 CAR-T cell therapy of relapsed/refractory solid tumors ± a CLDN6-encoding mRNA vaccine: Dose escalation data from the BNT211-01 phase 1 trial using an automated product.

Abstract

2518 Background: We are developing a chimeric antigen receptor (CAR)-T cell therapy targeting claudin 6 (CLDN6), an oncofetal antigen that is undetectable in healthy somatic tissue and highly expressed in various solid cancers. Autologous CLDN6 CAR-T cells are being tested alone and in combination with CLDN6-encoding CAR-T cell Amplifying RNA Vaccine (CARVac), a nanoparticulate RNA vaccine designed to stimulate and expand CLDN6 CAR-T cells. Methods: The ongoing first-in-human trial BNT211-01 evaluates the safety and feasibility of CLDN6 CAR-T cell transfer ± CARVac in lymphodepleted patients with relapsed/refractory solid tumors. Patients are pre-screened for CLDN6 expression with a cut-off of 50% positivity of intermediate or strong intensity by immunohistochemistry staining. Key endpoints are safety, tolerability, and anti-tumor activity. Pharmacokinetics of adoptively transferred CAR-T cells in peripheral blood is monitored by quantitative PCR. Dose escalation proceeds according to a classical 3+3 design, testing CLDN6 CAR-T cells at each dose level as both as monotherapy and in combination with CARVac. We previously reported results from 22 patients from 4 dose escalation cohorts with a manual CAR-T production process ± CARVac (ESMO-IO LBA38) which followed the same methodology. We observed durable responses along with a manageable safety profile, in line with commercial CAR-T products used to treat B-cell malignancies. No on-target/off-tumor toxicity and only a single case of (grade 1) neurotoxicity was observed. Given the encouraging efficacy, we have implemented an automated process to scale-up manufacturing. Accordingly, we are repeating the dose escalation with an automated CAR-T cell product, and with a modified CARVac regimen. As of 1st February 2023, 7 patients with epithelial ovarian carcinoma (EOC), 4 with testicular germ cell tumors (GCT), and a further 5 patients with tumors of various indications have been infused with CAR-T cells up to DL2. We intend to submit efficacy, safety and CAR T-cell pharmacokinetics data from 5 cohorts treated with 1x106, 1x107 or 1x108 CLDN6 CAR-T cells ± CARVac with a data cut-off of March 14th, 2023 from ≥17 treated patients as a late-breaking abstract. Clinical trial information: NCT04503278 .