Cambridge biotech raises $90 million for drug that uses radioactive atoms to fight prostate cancer

Convergent Therapeutics says its treatment precisely targets tumor cells while sparing healthy tissue.

Dr. Philip Kantoff is the chief executive of Convergent Therapeutics.Steph Stevens Photo

Radiation therapy has been used to treat cancer for more than a century, and about half of all cancer patients still undergo it at some point, according to the National Cancer Institute. Typically, patients receive beams of radiation from a machine that kills cancer cells inside their bodies but can also damage healthy tissue.

In the past decade, however, the Food and Drug Administration has approved several drugs called radiopharmaceuticals that use a more precise approach. Injected into the bloodstream, the medicines contain radioactive atoms that deliver radiation to targeted cells, attacking tumors while limiting damage to surrounding tissues.

On Wednesday, a Cambridge biotech making inroads in the growing field said it has raised $90 million in venture capital in its first fund-raising round. The startup, Convergent Therapeutics, plans to use the money to advance what it calls “next-generation radiopharmaceuticals,” including its lead program to combat advanced prostate cancer.

Dr. Philip Kantoff, Convergent’s chief executive and an oncologist, cited the blockbuster success of Novartis’s radiopharmaceutical Pluvicto. The FDA approved that treatment in 2022 after it prolonged the lives of patients with advanced prostate cancer in a pivotal study.

Demand for Pluvicto has so exceeded expectations that the Swiss drug giant recently had to stop adding new patients for the treatment. Last month, the FDA hastily authorized Novartis to use its manufacturing facility in Millburn, N.J., to help ramp up the supply of the medicine.

“Novartis opened up the field,” said Kantoff, who worked at the Dana-Farber Cancer Institute and Memorial Sloan Kettering Cancer Center in New York for about 35 years before leaving in 2021. “We think there’s a tremendous opportunity to expand on what they’ve done.”

Other than skin cancer, prostate cancer is the most common cancer in men in the United States, according to the American Cancer Society. The nonprofit estimates there will be more than 288,000 new cases this year and that about 34,700 men will die from it. One in eight men will be diagnosed with prostate cancer at some point. The risk increases with age, and the disease is more common in Black men.

Kantoff cofounded Convergent with Dr. Neil Bander, a professor of urologic oncology at Weill Cornell Medicine in New York. Bander is an authority on the biology of a protein on the surface of prostate cancer cells, called prostate-specific membrane antigen, or P.S.M.A. Convergent has licensed technology that Bander developed at Cornell University to target the protein.

Novartis’s radiopharmaceutical, Pluvicto, also targets P.S.M.A. But it uses a chemical compound known as a small molecule to deliver radiation-emitting particles that kill prostate cancer cells, Kantoff said. And the radiation comes in the form of beta particles.

In contrast, Convergent plans to use a protein in the immune system called antibodies to deliver radiation-emitting particles, and the radiation comes in the form of alpha particles, which Kantoff says are 1,000 times more powerful than beta particles.

Convergent has tested its radioantibody ― called CONV01-α ― on about 100 patients with advanced prostate cancer in early- and mid-stage trials, almost all at Weill Cornell Medicine, Kantoff said. Some patients received a single dose, while others got two.

The results, he said, have been very promising. They have been presented at three major conferences of cancer experts, including the American Society of Clinical Oncology, but have yet to be published in a medical journal and subjected to peer review. Convergent plans to begin a late-stage trial of a two-dose regimen by early 2025, and Kantoff said he hopes the clinical trial sites will include Harvard-affiliated teaching hospitals.

Dr. Felix Feng, a professor of radiation oncology, urology, and medicine at the University of California San Francisco, said the field of radiopharmaceuticals is taking off and Convergent’s approach is one of the most exciting.

“It represents one of the first alpha particle emitters that’s been introduced into the clinic,” he said. “The more radiation dose that’s delivered in a targeted manner, the more tumor kill” the treatment is likely to have, Feng said.

Convergent isn’t the only local startup working on radiotherapeutics. In February, Boston biotech Ratio Therapeutics said it had raised more than $40 million to develop similar cancer-fighting medicines.

Convergent’s fund-raising round was led by the venture capital firms OrbiMed and RA Capital Management, with participation from INVUS. Dr. Tal Zaks, a partner at OrbiMed and former chief medical officer of Cambridge-based Moderna, maker of a COVID-19 vaccine, said, “we believe that Convergent Therapeutics’ radioantibody approach is ideally suited to treat cancer and bring effective breakthrough treatments to patients.”