AACR 2015: Combining Two Investigational Immunotherapy Drugs Safe, With Early Signs of Effectiveness


Key Points

  • At a median follow-up of 22 months, metastatic melanoma patients treated with CP-870,893 and tremelimumab had an overall response rate of 27%, with complete responses in two patients and partial responses in four patients.
  • Median progression-free survival was 2.5 months, and the median overall survival was 26.1 months.
  • Researchers will next combine the anti-CD40 antibody with chemotherapy as an experimental neoadjuvant treatment for pancreatic cancer.

Combining the immunostimulatory anti-CD40 monoclonal antibody CP-870,893 with the immune checkpoint inhibitor tremelimumab was found to be safe, with clinical evidence of response in patients with advanced melanoma, according to phase I clinical trial data presented at the AACR Annual Meeting 2015, held April 18 to 22 in Philadelphia (Abstract CT137).

“If you think of the immune system like a bicycle, there are two broad ways of regulating the bike’s speed: pedaling and braking. To go faster, you can either pedal harder or release the brakes. In this case, we’ve attempted to stimulate the immune system both by pedaling faster, using the anti-CD40 antibody, and by cutting the brakes, using the anti–CTLA-4 antibody,” said David L. Bajor, MD, Instructor in the Division of Hematology/Oncology at Perelman School of Medicine at the University of Pennsylvania.

 “This novel combination of an immunostimulatory molecule and a checkpoint inhibitor was found to be safe. There was real concern that stimulating the immune system while ‘cutting the brakes’ with checkpoint inhibition could lead to increased incidence or severity of immune side effects. We did not see this,” said Dr. Bajor. “Secondarily, the clear clinical evidence of response to this combination, even in some patients with highly morbid visceral disease, was striking.”

Study Results

In this phase I dose-escalation trial, Dr. Bajor and colleagues enrolled 24 patients with metastatic melanoma who had never received an anti-CD40 or anti–CTLA-4 antibody before, and tested four different dose levels of the combination. Patients received tremelimumab every 12 weeks and the anti-CD40 antibody every 3 weeks until progression, toxicity, or 1 year of treatment elapsed.

After a median follow-up of 22 months, the overall response rate was 27%, which included complete responses in two patients and partial responses in four patients. The median progression-free survival was 2.5 months, and the median overall survival was 26.1 months.

The side effects were nonoverlapping and similar to those which had been seen when each of these agents was tested independently, according to Dr. Bajor. 

To see whether there was a correlation between treatment outcomes and changes in the patients’ immune cells to which the two drugs were targeted, the investigators analyzed CD8-positive T cells isolated from the patients’ blood, and found increases in biomarkers that were indicative of immune activation.

 “Immunotherapy is not just a single agent or class of agents; there are many targetable molecules to manipulate many facets of the immune responses against cancer. Checkpoint inhibition was just the beginning,” said Dr. Bajor.

The investigators will next combine anti-CD40 with chemotherapy as a neoadjuvant treatment for pancreatic cancer and study new anti-CD40 compounds. “Our upcoming trials are designed to expand our understanding of CD40 biology, and hopefully continue to broaden the spectrum of safe, effective treatments for patients,” he concluded.

This study was supported by a Penn-Pfizer alliance grant and the National Cancer Institute.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.