• Results from a late-stage study showed MacroGenics’ experimental drug margetuximab extended progression-free survival in previously treated HER-2 positive metastatic breast cancer patients over Roche’s Herceptin, when both were given alongside chemotherapy.
• Treatment with MacroGenics’ drug reduced the risk of disease worsening or death by 24% in the Phase 3 trial, the company said Wednesday. In a subgroup of patients carrying a certain genetic marker correlated with worse responses to Herceptin, the measured risk reduction climbed to 32%.
• Margetuximab’s safety and tolerability were “comparable to Herceptin when combined with chemotherapy,” the Maryland-based drugmaker said.

News of the trial success sent Macrogenics shares soaring higher by more than 130% Wednesday.

“This trial was always high-risk, and expectations were low — so this success is a big deal,” wrote Evercore ISI analyst Umer Raffat in a Feb. 6 note to investors. Raffat predicted the study could help drive the company’s market value above $2 billion.

Analysts at SVB Leerink had a rosier view of the study’s chances of success, previously modeling a 60% chance of success. Still, the results remove a “major overhang” for Macrogenics, analyst Jonathan Chang wrote Wednesday.

The results suggest margetuximab could be an option for patients who may be close to exhausting other therapies. All the patients in the study had previously been treated with Herceptin (trastuzumab) and Perjeta (pertuzumab), and about 90% had received Kadcyla (ado-trastuzumab emtansine) as well. All three drugs are sold by Roche.

Potential sales for this population of previously treated patients could reach about $400 million a year worldwide, according to Evercore ISI.

Based on the study, MacroGenics said it expects to submit a Biologics License Application for margetuximab to the Food and Drug Administration in the second half of this year.

No data is yet available, however, on whether Macrogenics’ drug helps to extend overall survival versus Herceptin when used with chemotherapy. A follow-up analysis is ongoing, Macrogenics said.

Margetuximab is the most advanced drug candidate in MacroGenics’ pipeline, which is primarily focused in oncology.