BOSTON – CT053, a chimeric antigen receptor (CAR) T-cell therapy, has demonstrated efficacy and tolerability in a phase 1 trial of patients with relapsed/refractory multiple myeloma.
CT053 produced an objective response rate of 87.5% and a complete response rate of 79.2%. All patients experienced grade 3 or higher adverse events (AEs), but none developed grade 3 or higher cytokine-release syndrome (CRS).
Siguo Hao, MD, of Xinhua Hospital, Shanghai (China) Jiaotong University, presented these results at the International Myeloma Workshop held by the International Myeloma Society.
Dr. Hao explained that CT053 consists of autologous T cells modified with a second-generation CAR that incorporates a fully human anti–B-cell maturation antigen single-chain fragment variant, a 4-1BB costimulatory domain, and a CD3-zeta–signaling domain.
In preclinical studies, CT053 induced dose-dependent cytotoxic effects on multiple myeloma cell lines and completely eradicated myeloma in mice.
Dr. Hao and his colleagues conducted the phase 1 study of CT053 at three sites (, , and ). The study enrolled 30 patients with relapsed/refractory multiple myeloma, and 24 ultimately received CT053.
In the 24 patients, the median age was 60.2 years (range, 38.5-70.0 years), and the median time since diagnosis was 3.5 years (range, 0.3-10.8 years). Nine patients had progressive disease at baseline.
The patients had received a median of 5 prior therapies (range, 2-12). All patients had received a proteasome inhibitor, 22 had received an immunomodulatory agent, 10 had undergone a transplant, and 5 had received an anti-CD38 monoclonal antibody.
For this study, patients received conditioning with fludarabine and cyclophosphamide, followed by a single infusion of CT053. Most patients (n = 21) received 1.5 x 108 cells, but three received 0.5 x 108, 1 x 108, and 1.8 x 108 cells, respectively.
The median follow-up was 333 days. CAR T cells were detectable 1-7 days after infusion and peaked at 7-21 days. The cells persisted for a median of 172 days (range, 21-341 days).
A total of 21 patients responded to treatment (87.5%). There were 19 patients with a complete response or stringent complete response, 1 patient with a very good partial response, and 1 with a partial response.
Dr. Hao noted that CT053 was effective even at the lowest dose. The patient who received 0.5 x 108 cells initially achieved a very good partial response that deepened to a stringent complete response on day 502 after infusion.
Ten patients still had a stringent complete response at last follow-up, and two had a complete response. Nine patients progressed, and one patient relapsed after achieving a complete response. Three patients died, two from disease progression and one from a serious AE (neutropenic infection).
All 24 patients experienced a treatment-related AE, and all had grade 3 or higher hematologic AEs. Six patients had grade 3 or higher fever, six had grade 3 or higher infections and infestations, and one had grade 3 or higher neurotoxicity.
Three patients had grade 1 CRS, and 12 had grade 2 CRS. None of the patients had grade 3 or higher CRS.
This trial was sponsored by Xinhua Hospital/Shanghai Jiao Tong University School of Medicine, First Affiliated Hospital of Zhejiang University, and First Affiliated Hospital of Wenzhou Medical University in collaboration with Carsgen Therapeutics. Dr. Hao did not disclose any conflicts of interest.
SOURCE: Hao S et al. IMW 2019,