ImmunoGen announces the presentation of positive trastuzumab-DM1 clinical data

“We’re thrilled with the clinical data reported today,” commented Daniel Junius, ImmunoGen President and CEO. “It’s deeply gratifying to see so many patients respond to T-DM1, particularly when one considers that their cancer previously had been treated with the two approved HER2-targeting agents as well as with multiple chemotherapies. ImmunoGen’s goal in developing our Targeted Antibody Payload, or TAP, technology was to enable the achievement of significant new anticancer therapies, both by us and by our partners. We believe the data reported today are a major step forward in the realization of this vision.”

The findings presented were from a 110-patient Phase II trial assessing T-DM1 for the treatment of advanced (metastatic) HER2-positive breast cancer. To qualify for enrollment, patients must have undergone prior treatment with regimens that included an anthracycline, a taxane, trastuzumab (Herceptin®), lapatinib (Tykerb®) and capecitabine (Xeloda®).

Among the data reported were:

• The T-DM1 objective response rate (ORR) was 32.7%, as assessed by an independent review facility (IRF). ORR is the proportion of study patients who had a durable complete or partial response to treatment with T-DM1, and was the primary endpoint of the study.
• The clinical benefit rate (CBR) was 44.5%, as assessed by an IRF. CBR includes patients who had stable disease for six months or longer as well as patients who had an objective response to T-DM1.
• Duration of response and progression-free survival (PFS) data are not yet mature. The median PFS reported was 7.3 months, and updated, mature data will be presented at a future meeting.
• Among patients who had centrally-confirmed HER2-positive cancer, the ORR was 39.5% and the CBR was 52.6%, as assessed by an IRF.
• Among the patients who had qualified for the trial as HER2-positive by local assessment, but were HER2-normal by central assessment, the ORR was 20.0% and the CBR was 26.7%.

The toxicities reported were considered to be acceptable, manageable and consistent with those reported in other T-DM1 trials. The most common severe adverse events were thrombocytopenia (5.5 percent) and back pain (3.6 percent), and the most common adverse events were fatigue (59.1 percent) and nausea (37.3 percent). One patient with pre-existing non-alcoholic fatty liver disease and multiple co-morbidities died from hepatic dysfunction.