FDA grants breakthrough status to novel therapy for hard-to-treat CML
Merck to acquire cancer treatment's developer in cash deal worth billions
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The U.S. Food and Drug Administration (FDA) has named Terns Pharmaceuticals’ investigational oral agent TERN-701 a breakthrough therapy for potential use in certain people with chronic myeloid leukemia (CML), a form of blood cancer.
The new designation specifically covers the use of TERN-701 in people with CML whose cancer carries a genetic abnormality called the Philadelphia chromosome but does not have another mutation called T315I. The treatment candidate is specifically indicated for individuals whose CML is in its chronic phase, the earliest stage of disease where progression is slow and symptoms are minimal, and who have tried at least two other tyrosine kinase inhibitors.
The FDA awards breakthrough designation to experimental treatments that, based on early trial data, have the potential to meaningfully improve care for people with serious diseases.
The new status comes on the heels of a recent announcement that pharma giant Merck will acquire Terns in a cash deal valued at roughly $6.7 billion.
“This Breakthrough Therapy Designation, along with the recent agreement for Merck to acquire Terns, has the potential to accelerate efforts to advance TERN-701 to a pivotal trial and to patients,” Amy Burroughs, CEO of Terns, said in a company press release announcing the new status.
“This is an exciting time for everyone involved in the TERN-701 program,” Burroughs said. “We are grateful to the investigators, patients and community advocates whose dedication and support have made these advancements possible.”
CML is a form of blood cancer marked by the abnormal growth of certain immune cells. In many cases of CML, abnormal cancer growth is driven by a specific genetic abnormality called the Philadelphia chromosome, leading to the production of an abnormal fusion protein called BCR::ABL1 that drives cancer growth.
Tyrosine kinase inhibitors, or TKIs, are a class of treatments that primarily block the activity of this mutant protein.
75% of leukemia patients in trial saw response to therapy
TERN-701 is a novel TKI designed to target the fusion protein with a potentially best-in-class profile that could maximize effectiveness and safety, according to Terns.
“There remains an urgent need for CML treatments that offer improved efficacy, safety, and tolerability over current therapies,” said Scott Harris, chief development and operations officer at Terns.
Harris added that the new FDA designation “supports the significant potential of TERN-701 to be a best-in-disease therapy for CML patients and offer substantial improvement based on the faster, deeper responses compared to prior TKIs and encouraging safety and tolerability profile observed to date.”
The FDA’s decision to grant breakthrough designation to TERN-701 was based mainly on data from an ongoing Phase 1/2 clinical trial called CARDINAL (NCT06163430), which is testing the therapy in adults with CML who had an inadequate response to at least one prior TKI. The trial is actively recruiting participants at sites in the U.S., South Korea, New Zealand, and Australia, as well as in several nations in Europe.
As of June 2025, 75% of the 32 patients evaluable for efficacy had achieved a major molecular response by 24 weeks, or about 5.5 months. The company noted that responses have been seen in patients who entered the trial with a high disease burden and who had previously received multiple lines of therapy. The company also said that there have not been many serious safety issues or treatment discontinuation.
