Dynavax Technologies Corp. said a treatment combining its lead drug candidate SD-101 and Merck & Co. Inc.'s Keytruda was well tolerated by skin cancer patients in an early stage study.
Keytruda targets the PD-1 and PD-L1 proteins, preventing cancer cells from evading the immune responses SD-101 is designed to trigger. SD-101 is a TLR-9 agonist which activates and helps mature immune cells.
The results are from an ongoing phase 1b/2 trial, dubbed Keynote-184, which enrolled 69 patients with advanced melanoma — one of the deadliest forms of skin cancer. The main goals of the trial are to find whether using SD-101 in combination with Keytruda is safe and effective.
Dynavax said 39 patients received Keytruda with 8 milligrams of SD-101, while 30 patients received only up to 2 mg.
Adverse events related to the treatment were transient, with mild to moderate flu-like symptoms.

In the high-dose group, 38% of patients responded to treatment, meaning their tumors shrunk due to SD-101 and Keytruda.
Meanwhile, 70% of participants in the low-dose group responded to therapy, with 17% having no detectable cancer after treatment. Cancer did not progress after six months for 74% of the patients who responded to SD-101 and Keytruda.
"We are moving forward with the 2 mg dose of SD-101 for our phase 3 trial which we believe is the optimal dose," Dynavax Chief Medical Officer Rob Janssen said in a news release.
SD-101 is being tested in combination with Keytruda in patients with advanced melanoma and in patients with head and neck squamous cell cancer. The California-based biotech retains all commercial rights to SD-101.
The 2018 American Society of Clinical Oncology meeting is expected to bring together more than 32,000 professionals from all over the world, with more than 2,500 study abstracts to be presented on site and an additional 3,350 abstracts to be published online.
