Sellas Life Sciences’ investigational CDK9 inhibitor has scored in a midstage acute myeloid leukemia (AML) study, demonstrating an overall response rate (ORR) more than double the 20% goal.
The open-label, single-arm trial studying Sellas’ small molecule met all primary endpoints, with survival outcomes exceeding both the biotech’s targeted expectations and historical benchmarks, according to a July 15 release.
The phase 1/2a study centers around SLS009, also known as tambiciclib, a CDK9 inhibitor being studied in combination with venetoclax—sold as Venclexta and Venclyxto—and chemotherapy Vidaza.
The phase 2 portion of the trial included 54 evaluable patients with advanced AML who hadn’t previously responded to venetoclax therapies.
Among the 54 patients, 87% had AML-myelodysplasia-related changes (AML MR), a common subtype of the leukemia, while 43% had ASXL1 mutations, which is often linked to poor prognosis in myeloid diseases.
SLS009 was delivered at two dose levels, 45 mg and 60 mg, with patients in the higher dose cohort receiving either a 60 mg dose once a week or a 30 mg dose twice per week.
Sellas said the primary endpoint for the phase 2 portion of the trial was ORR, with secondary endpoints including overall survival (OS), safety and tolerability.
While the trial had no standard-of-care or placebo arm, Sellas set an ORR target of 20%, plus a target median survival of at least three months.
The New York-based biotech reported a 44% ORR for patients with AML MR who received 30 mg twice a week, while patients with the AML MR myelomonocytic/myelomonoblastic (M4/M5) subtype experienced an ORR of 50%.
A 50% response rate was also recorded for patients with ASXL1 mutations in the 30 mg twice weekly arm. Across all evaluable patients, ORR was 33%, Sellas said.
Meanwhile, an 8.9 month median overall survival (mOS) rate was recorded for patients with AML MR.
Patients who had a median of one prior line of therapy and received 30 mg twice weekly experienced a mOS of 8.8 months. That compares with the historical benchmark of 2.4 months for patients with second-line AML receiving the best available therapy, Sellas said.
For patients receiving two prior lines of therapy, the mOS was 4.1 months versus the 1.8 month-benchmark for best available therapy.
On the safety side, no dose-limiting toxicities were observed and a similar toxicity profile associated with just venetoclax and chemotherapy was observed.
Based on the data and following the FDA’s recommendation, Sellas is moving SLS009 into a randomized trial that will include newly diagnosed AML patients. According to the biotech, the federal agency believes clinical benefit may be greatest for first-line AML patients. The study is designed to support a potential new drug application, Sellas said.
The company expects to launch the 80-patient study by the first quarter of next year.
“These SLS009 results represent an important advancement for patients with relapsed/refractory AML, where treatment options remain limited and outcomes are often poor,” Yair Levy, M.D., director of hematologic malignancies research at Texas Oncology Baylor University Medical Center, said in the release. “The response rates and survival outcomes are particularly compelling, especially given the consistency of responses across high-risk molecular subtypes and the favorable safety profile.”
While Sellas’ stock spiked in premarket trading this morning, the biotech’s share price was up only 2% at around $2 per share as of 11:00 a.m. ET.