BioSight, Ltd, a pharmaceutical development company, focused on the development of targeted oncology therapeutics with reduced toxicity, announced completion of last patient treatment in its extended phase I/II clinical study of BST-236 (Astarabine) in acute leukemia patients. The company expects to report top-line results of the study in the coming months.

The phase I/II clinical trial is a dose-escalation open-label single arm study to evaluate the safety and efficacy of BST-236 as a single agent in adults with Acute Myeloid Leukemia (AML) or Acute Lymphoblastic Leukemia (ALL). The study, extended by additional dose-escalating cohorts, enrolled overall 26 patients, either relapsed/refractory or older newly-diagnosed unfit for standard therapy.

BST-236 was well tolerated at all doses and patient groups, including in the older and unfit newly-diagnosed AML patients (median age 79, range 70-90 years). Furthermore, BST-236 treatment achieved high response rates in the older and unfit newly-diagnosed AML patients, accompanied by a considerably prolonged survival.
“The timely completion of patient enrollment and treatment in this acute leukemia trial marks an important milestone in the development of BST-236” said Dr. Ruth Ben Yakar, CEO of BioSight. “In light of the promising preliminary results obtained to date, we look forward to presenting top-line data of the BST-236 Phase I/II clinical trial in the coming months”.

BST-236 is a novel compound of cytarabine covalently bound to asparagine. It acts as a pro-drug of cytarabine, designed to deliver high cytarabine doses to leukemia cells. Cytarabine is the first-line treatment for AML and relapsed/refractory ALL since the 1970’s, however it is highly toxic with severe side effects such as bone marrow suppression and cerebellar and gastrointestinal toxicities. Therefore, while the average age of AML patients is almost 70 years, cytarabine doses are significantly attenuated for older patients and for patients with liver and kidney dysfunction, resulting in poor outcomes. Unlike cytarabine, the toxicity of BST-236 is targeted to leukemia cells, resulting in lower systemic exposure to free cytarabine. Inside the leukemia blasts, BST-236 is cleaved to cytarabine, enabling targeted killing and relative sparing of normal tissues. As such, BST-236 may serve as an ideal therapy for leukemia, particularly for delivering high doses of cytarabine to medically unfit or older adults who otherwise may mainly be treated with reduced intensity or supportive therapy with poor outcomes.