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Proof-of-Concept Trial of BTK Inhibitor in Advanced B-Cell Malignancies

By: Kayci Reyer
Posted: Tuesday, January 7, 2020

According to early-phase research presented at the 2019 American Society of Hematology (ASH) Annual Meeting & Exposition in Orlando, Florida (Abstract 501), the Bruton’s tyrosine kinase (BTK) inhibitor LOXO-305 appears to be effective and tolerable in patients with advanced B-cell malignancies. The first-in-human phase I trial included patients who had undergone at least two previous therapies.

“Phase I data with LOXO-305 demonstrate a favorable safety profile and provide proof-of-concept evidence of efficacy in heavily pretreated [chronic lymphocytic leukemia] and [mantle cell lymphoma] patients, including patients with acquired resistance to available BTK inhibitors and venetoclax,” concluded Anthony R. Mato, MD, MSCE, of Memorial Sloan Kettering Cancer Center, New York, and colleagues.

The study included nine patients with chronic lymphocytic leukemia (CLL) and four with mantle cell lymphoma. Participants received daily oral LOXO-305 in 28-day cycles in 25-mg (n = 5), 50-mg (n = 5), or 100-mg (n = 3) doses. All study patients had received a median of three prior treatments, including chemotherapy plus an anti-CD20 antibody (n = 12), autologous stem cell transplantation (n = 2), umbralisib (n = 5), ibrutinib (n = 10), and venetoclax (n = 1).

During the initial treatment cycle, clinical activity was observed, including in patients receiving the lowest daily dose of 25 mg. Of the eight patients evaluable for initial response, seven experienced a tumor response (87.5%). Evaluable patients with CLL achieved a partial response (n = 1) or a partial response with lymphocytosis (n = 4), whereas evaluable patients with mantle cell lymphoma achieved a partial response (n = 2) or experienced disease progression (n = 1). No dose-limiting toxicities were reported, and just grade 1 or 2 treatment-emergent adverse events were observed.

Disclosure: For full disclosures of the study authors, visit ash.confex.com.



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