Time runs out for Kronos' phase 3 AML drug as biotech blames enrollment struggles for ending trial

While the biotech bear market has forced many companies to trim their pipelines, it’s less common to see a late-stage asset thrown on the scrapheap. But Kronos Bio has made that call for its acute myeloid leukemia (AML) drug entospletinib.

The biotech will discontinue the phase 3 trial of its spleen tyrosine kinase (SYK) inhibitor entospletinib for the treatment of newly diagnosed patients with NPM1-mutated AML. The company stressed the decision had been made due to enrollment difficulties rather than reports of any adverse events or lack of efficacy.

The study, which kicked off in November 2021 and was due to run into 2026, aimed to enroll 180 participants across sites in the U.S., Canada, Brazil, South Korea, Israel and various countries in Europe, according to ClinicalTrials.gov.

“The company projected significant delays due to several factors, including the operational challenges the company faced in enrolling a genetically defined subset of patients in a front-line setting, the residual and ongoing impacts of the COVID-19 pandemic, and the inability to activate planned clinical trial sites in Russia and Ukraine,” Kronos said in a statement released ahead of its third-quarter earnings.

It doesn’t mean Kronos has given up on trying to treat AML by inhibiting SYK. One of the two assets being prioritizing in the company's revamped strategy is the SYK inhibitor lanraplenib, which is currently being assessed in combination with Astellas’ Xospata in a phase 1b/2 trial for relapsed/refractory AML.

Unlike entospletinib, which requires twice-daily dosing, lanraplenib can be administered once a day and can be taken either with food or when fasting, Kronos pointed out. Lanraplenib may also be co-administered with proton-pump inhibitors for patients who require management of their gastro-esophageal reflux or related conditions.

Kronos’ other lead asset is the CDK9 inhibitor KB-0742, which is currently in a phase 1/2 trial in patients with solid tumors, with a planned update due before the end of the year. Once a dose level has been decided on, the company plans to expand the trial to cover patients with MYC-amplified solid tumors and patients with transcriptionally addicted cancers.

CEO Norbert Bischofberger, Ph.D., a former head of R&D at Gilead Sciences who took the helm at Kronos in 2018, said the strategic rethink was “the right decision at the right time.”

“Focusing on lanraplenib and KB-0742 will allow us to direct our resources to the highest value programs and deliver on our mission of bringing cancer drugs to the patients with the greatest need,” Bischofberger said in the release. “It makes us a stronger company as a result.”

This pipeline prioritization is expected to extend Kronos’ cash runway from the fourth quarter of 2024 into the second quarter of 2025. The California-based biotech had $270 million in cash and equivalents as of the end of September.