SELLAS Life Sciences’ CDK9 inhibitor, SLS009, for relapsed/refractory acute myeloid leukaemia (r/r AML) is set to advance after it met all endpoints in a Phase Ia/II trial.
The open-label Phase Ia/II study (NCT04588922) was evaluating the safety, tolerability, and efficacy of SLS009 (tambiciclib) in combination with Venclexta (venetoclax) and Vidaza (azacitidine) at two dose levels, 45mg and 60mg. In the 60mg dose cohort, patients were treated with either a 60mg dose once per week or a 30mg dose two times per week. The 54 patients enrolled had previously not responded to Venclexta.
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SELLAS said the study “exceeded expectations”, with a mean overall response rate (ORR) of 33%, exceeding the threshold of 20%. ORR was the study’s primary endpoint.
When looking at certain arms, some benefited from even higher ORR. For example, AML patients with myelodysplasia-related changes who received 30mg twice weekly had a 44% ORR. The highest ORR was reached by patients with ASXL1 mutations, with an ORR of 50% and acute myelomonocytic leukaemia (AML-M4) and acute monocytic leukaemia (AML-M5) patients, also with 50%.
In regard to overall survival (OS), patients with AML MR achieved 8.9 months, and patients with r/r AML who received one prior line of therapy and received twice weekly SLS009 reached 8.8 months. Both these targets surpassed the historical benchmark of 2.4 months and the 3-month target set by investigators.
For patients who had received two previous lines of therapy, OS was 4.1 months compared to the 1.8-month benchmark.
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By GlobalDataThe treatment was also well-tolerated, with no dose-limiting toxicities across any treatment arm.
As a result of the Phase II study, SELLAS will advance SLS009 to a randomised trial that will expand into the newly diagnosed AML populations, as well as patients who are resistant to prior Venclexta and Vidaza treatment. The study will support a potential New Drug Application (NDA) with the US Food and Drug Administration (FDA).
CEO of SELLAS Dr. Angelos Stergiou, said: “The remarkable response rates of 44% among AML MR patients, 50% among ASXL1-mutated AML MR, and 50% among M4/M5 patients at the optimal 30mg twice weekly dose far exceed the targeted 20% benchmark. We believe these data strongly support the potential of SLS009 to meaningfully extend life in patients with otherwise limited options, and we look forward to sharing these findings in more detail in the future.”
SELLAS is also investigating SLS009 in r/r diffuse large B-cell lymphoma (DLBCL) and r/r peripheral T-cell lymphoma.
Also in SELLAS’ pipeline is galinpepimut-S, a cancer vaccine being investigated in the Phase III REGAL study (NCT04229979) in patients with AML second complete remission (CR2) or second complete remission with incomplete platelet recovery (CRp2). The REGAL study is expected to be completed by the end of 2025.
