Lead Syndax Drug Shows Survival Benefits in Breast Cancer Trial

Xconomy Boston — 

Just two months after reporting positive data from a clinical trial of its lead drug candidate in lung cancer, Waltham, MA-based Syndax said today that the same drug performed well in a Phase 2 breast cancer trial. Results from the trial of the drug, called entinostat, will be presented at the American Society of Clinical Oncology (ASCO) Breast Cancer Symposium this week in San Francisco.

The drug was tested in 130 postmenopausal women with a type of the disease known as estrogen receptor-positive breast cancer. The women received either entinostat plus exemestane (Aromasin, made by Pfizer) or exemestane plus placebo. The combination containing Syndax’s drug nearly doubled the amount of time women survived without their disease progressing—from 2.3 months to 4.3 months. Although such “progression-free survival” was the primary endpoint, the study also showed that overall survival increased by nearly seven months, to a total of 26.9 months.

Syndax is pursuing drugs designed around epigenetics—the molecular changes in cells that can activate or de-activate genes without affecting the underlying DNA. Entinostat inhibits certain enzymes that influence specific epigenetic alterations. Those epigenetic alterations are believed to drive cancer growth and drug tolerance, so blocking them should enhance cancer treatment, Syndax’s researchers believe.

The results were a pleasant surprise for Syndax’s CEO, Joanna Horobin, who trained as a physician before joining the drug industry 25 years ago. “The study was not powered around overall survival, but it is still significant to see a seven-month benefit there,” she says. Based on the positive results from the trial, Syndax plans to start a pivotal Phase 3 trial in early 2012.

Syndax has also identified a biomarker that seems to indicate whether patients with breast cancer are responding to entinostat. The trial demonstrated that median progression-free survival rates in women with that biomarker increased to over six months. “Rather than waiting eight weeks to take a scan to see if it’s working, we can take a blood sample before the treatment, then at day one, day eight, and day 15,” Horobin says. “Then we can see if the drug is impacting the target.” Syndax will incorporate biomarker testing into the Phase 3 trials, she says.

If all goes well with the Phase 3 program, Horobin adds, entinostat could become the first epigenetic therapy approved for patients with solid tumors. “There hasn’t been much to improve the therapies available to breast cancer patients,” Horobin says. “I, as a physician, find this opportunity really exciting.”