Loxo Oncology Stocks Jump After Positive Data Released at ASCO Preview

In after-hours trading, Loxo Oncology shares climbed 19 percent after data for its cancer drug LOXO-292 was released in a preview of abstracts for the upcoming American Society of Clinical Oncology (ASCO) meeting.

LOXO-292 targets tumors with mutations in the RET gene. In an ongoing Phase I clinical trial, the drug showed almost 70 percent of patients, regardless of cancer origin, had tumor shrinkage. It appeared to be well tolerated by patients with advanced cancer. Many of the trial participants were resistant to available treatments or were no longer responding to treatment.

The drug targets RET fusions, where two genes are fused together, which stimulates tumor growth. RET fusions are acquired mutations, rather than inherited, and are found in about two percent of lung cancers, 10 to 20 percent of papillary thyroid cancers, and in some other cancers. Reuters notes, “Other mutations known as activating RET point mutations account for about 60 percent of medullary thyroid cancers, which comprise three percent of all thyroid cancers.”

In the study, at least for data published in the abstract, 60 percent of evaluable patients had significant tumor shrinking. The overall response for patients with non-small cell lung cancer (NSCLC) was 65 percent, including three patients whose cancer had metastasized to the brain, and 83 percent of patients diagnosed with papillary thyroid cancer. Of patients with medullary thyroid cancers, about 79 percent showed tumor shrinkage ranging from nine to 45 percent.

In a conference call with analysts earlier this month, company chief executive officer Josh Bilenker said he was “encouraged by the data we submitted in January,” but also observed that the efficacy data had improved since January.

The news was a blow to Blueprint Medicines, which is also developing a RET inhibitor. Blueprint’s drug had an overall response rate of 37 percent, including 45 percent for NSCLC and 32 percent for medullary thyroid cancers. In after-hours trading, Blueprint shares dropped 13 percent.

Due to conference deadlines, the abstracts detailed data up to January 5.

Because these are early-stage trials, investors may be over-eager. It’s not yet clear if these data, which are preliminary in an early trial, are accurate reflections of the drugs, although they certainly sound promising. In April, Blueprint released data from its Phase I trial of BLU-667, indicating an overall response rate (ORR) of 45 percent, slightly below the 52 percent seen in the Loxo clinical trial. Within subpopulations, the variations were more notable, particularly a 19 percent different in ORR in NSCLC patients. But since the trials were not head-to-head comparisons, and the data is incomplete, it’s not really possible to make accurate comparisons.

Both Exelixis and Sanofi market drugs that appear to affect RET fusions. Exelixis’ Cabometyx is indicated for patients with advanced renal cell carcinoma. Sanofi’s Caprelsa is prescribed for medullary thyroid cancer (MTC).

Loxo is presenting two abstracts at the ASCO conference. One is “A Phase I Study of LOXO-292, A Potent and Highly Selective RET Inhibitor, in Patients with RET-Altered Cancers,” and the other is “Detection and Clearance of RET Variants in Plasma Cell-Free DNA (cfDNA) from Patients (pts) Treated with LOXO-292.”