CHICAGO – Agents that target the HER2, BRAF, Hedgehog, or EGFR pathways show promise in nonindicated tumor types that harbor these molecular alterations, according to early findings from the MyPathway study.
Of 129 patients enrolled in the multicenter, open-label, phase IIa study, 29 had a major response, defined as tumor shrinkage of at least 30%, to such treatment. One of those patients had a complete response, and 28 had a partial response. An additional 40 patients had stable disease on treatment. Fourteen of the 29 patients progressed after a median of 6 months’ follow-up, and 15 responses were ongoing at up to 11 months, Dr. John D. Hainsworth reported at the annual meeting of the American Society of Clinical Oncology.
No new safety signals were observed, said Dr. Hainsworth of Sarah Cannon Research Institute in Nashville, Tenn.
Treatments evaluated in MyPathway included:
• Trastuzumab + pertuzumab, which targets the HER2 pathway and is currently indicated for breast cancer.
• Vemurafenib, which targets the BRAF pathway and is currently indicated for melanoma.
• Vismodegib, which targets the Hedgehog pathway and is currently indicated for basal cell carcinoma of the skin.
• Erlotinib, which targets the EGFR pathway and is indicated for non–small-cell lung cancer.
Responses have been seen with all four of the treatments, but the best responses were seen among patients with HER2 and BRAF abnormalities.
Among 61 cancers with HER2 amplification/overexpression, trastuzumab + pertuzumab provided a benefit for colorectal, bladder, biliary, non–small-cell lung, pancreas, and head/neck cancers.
Of 20 colorectal tumors, 7 (35%) showed complete or partial response, and 3 (15%) remained stable for at least 120 days (clinical benefit rate, 50%). Complete/partial responses and stable disease, respectively, were also seen in three and two of eight bladder tumors (clinical benefit rate, 63%), in three and three of six biliary tumors (clinical benefit rate, 100%), in two and zero of seven non–small-cell lung tumors (clinical benefit rate, 29%), one and zero of six pancreas tumors (clinical benefit rate, 17%), and one and zero of three head and neck tumors (34%). One of 11 other types of tumors showed disease stability at 120 days (clinical benefit rate, 9%). The overall clinical benefit rate in the study was 43%, Dr. Hainsworth said.
Among 33 cancers with the BRAF mutation, vemurafenib showed activity for non–small-cell lung, ovary, unknown primary, colorectal, pancreas, and head/neck tumors. Of 15 non–small-cell lung tumors, 3 (20%) showed complete or partial responses and 2 (13%) remained stable for at least 120 days (clinical benefit rate, 33%). Complete/partial responses and stable disease, respectively, were also seen in one and two of four ovary tumors (clinical benefit rate, 75%), and complete or partial responses were seen in one each of three unknown primary tumors, two colorectal tumors, two pancreas tumors, and one head/neck tumor (clinical benefit rates of 33%, 50%, 50%, and 100%, respectively). No benefit was seen with tumors at other sites (total clinical benefit rate, 36%), Dr. Hainsworth said.
“Of interest in this group [of patients with BRAF mutations], seven of the eight responses were in V600E mutations, and as you know, that’s the mutation that’s been specifically correlated with high response to BRAF inhibition in melanoma where this treatment is now approved,” he said, adding that the response rate in those patients was 38%.
Based on these early results, enrollment of patients with HER2 abnormalities and colorectal, bladder, or biliary cancer, and of patients with BRAF mutations and lung cancer, will be expanded, he said.
Subjects enrolled in MyPathway have advanced cancer showing abnormalities in any of the pathways of interest. The first 129 received a mean of three prior therapies, and in the 29 who responded, 12 different types of cancer responded to the targeted treatment.
“An increasing number of targeted agents for advanced cancer are in use now based on the presence of molecular abnormalities in the cancer. … We’ve known that the same mutations that are in those cancers are found in a wide variety of other cancers, although at a lower incidence, and it’s been difficult to test how effective these same treatments are for the other cancers due to the difficulty in identifying the patient population,” he said, explaining that an increase in comprehensive genomic profiling in recent years has allowed for identification of more and more of these mutations in other cancers.
“I think we’ve shown now that this trial design is feasible, where patients are selected on the basis of molecular abnormalities in their cancers rather than on their primary tumor type or primary site, and certainly offers opportunities for patients with these molecular abnormalities,” Dr. Hainsworth concluded.