Loxo Oncology Inc. said LOXO-292 demonstrated durable efficacy in a phase 1/2 trial in patients with thyroid cancer.

The company reported updated interim data from a study called Libretto-001, which comprised an early stage dose escalation phase and a midstage dose expansion phase.

Stamford, Conn.-based Loxo Oncology reported the updated interim data at the American Thyroid Association's annual meeting. The biopharmaceutical company previously reported positive initial data from Libretto-001 at the 2018 American Society of Clinical Oncology meeting.

Data from the phase 2 portion covered 38 heavily pretreated patients — 29 with medullary thyroid cancer, or MTC, and nine with thyroid cancer, or TC.

All patients had tumors with rearranged during transfection, or RET, fusions and mutations. LOXO-292 inhibits native RET signaling and resistance mechanisms that could otherwise limit cancer drug activity.

LOXO-292 was given in 160-milligram doses. A dose exploration at 200 milligrams is also ongoing.

Of the 29 MTC patients, 17, or 59%, have responded to treatment. Two of these patients had no detectable cancer, and the rest saw a reduction in their tumor size.

Loxo Oncology said 16 of these 17 patients remain on therapy, with median follow-up of 8.4 months.

Of the 9 TC patients, 7, or 78%, have responded to treatment, with all experiencing tumor shrinkage.

Loxo Oncology said all of these patients remain on therapy, with median follow-up of 8.5 months.

According to the safety analysis, adverse events in the 82 patients who received LOXO-292 were mostly mild.

The U.S. Food and Drug Administration granted LOXO-292 breakthrough-therapy status in September.