After banking $78.5 million six months ago, Silverback Therapeutics is back for more. The immuno-oncology biotech is picking up another $85 million to advance its lead antibody-drug conjugate (ADC) through the clinic and to develop its earlier-stage pipeline.
Unlike other ADCs designed to kill cancer cells, Silverback is working on treatments that ramp up the body’s immune response to cancer. Its work is based on its ImmunoTAC platform, which attaches antibodies to small molecules that adjust the immune system, instead of cytotoxic, or cell-killing, drugs. This approach allows Silverback to target pathways that have previously been out of reach for small molecules because of their side effects.
“There are a number of pathways known to undergird the pathophysiology of various disease. But due to systemic toxicity associated with administering small molecules—and in some cases, antibodies, against those pathways—there hasn’t been a way to advance a therapy that appropriately targets or covers those pathways,” said Valerie Odegard, Ph.D., Silverback president and chief scientific officer, in a previous interview.
The company’s lead program, SBT6050, is an ADC that targets TLR8 in tumors that express the HER2 gene. The antibody makes sure the payload is delivered only to the HER2-expressing cancer cells, while the TLR8 agonist activates immune cells called myeloid cells to attack the tumor and “reprogram” the tumor microenvironment.
It’s an improvement on previous efforts with TLR8 agonists, which have been delivered systemically and lead to side effects that limit the amount of drug a patient can take, Odegard said.
SBT6050 is not the first drug of its kind to target HER2-positive cancers—Genentech’s Kadcyla has been available for years, getting its first approval for late-stage, HER2-positive breast cancer in 2013—but it could come in handy for patients who relapse after receiving Herceptin, Perjeta and Kadcyla.
The new funding will also push forward Silverback’s other ImmunoTAC programs, including an ADC aimed at Nectin-4—the target of Seattle Genetics’ bladder cancer ADC Padcev—in HER2-positive cancers, and undisclosed programs in cancer, virology and fibrosis. EcoR1 Capital led the series C round, with the likes of Orbimed, U.S. Venture Partners, Boxer Capital and Fidelity also chipping in.
Along with the financing, Silverback announced a pair of promotions: Odegard, who’s served as chief scientific officer since 2018, adds president to her title, while Naomi Hunder, M.D., becomes chief medical officer. Hunder joined the company last year as senior vice president of clinical research and development after holding similar roles at Acerta Pharma and Seattle Genetics.