Silverback Therapeutics is on a roll. After banking more than $160 million in venture capital this year, the immuno-oncology biotech filed on Tuesday to raise up to $100 million in its Wall Street debut. The funds will bankroll early-phase trials for its lead antibody-drug conjugate and preclinical work for its other programs.
The lead program, SBT6050, targets TLR8 in solid 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.
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It’s an improvement on previous efforts with TLR8 agonists, which must be given systemically and cause side effects that can limit the amount of drug a patient can take, Valerie Odegard, Ph.D., Silverback president and chief scientific officer, in a previous interview.
Silverback plans to fund the ongoing phase 1 study with the IPO proceeds, including an expansion into specific tumors and a phase 1b study in combination with a PD-1 inhibitor.
The funds will also push a second program toward an IND filing in the fourth quarter of 2021 and into phase 1, according to a securities filing. The treatment, SBT6290, also targets TLR8, but in solid tumors expressing Nectin4 rather than HER2.
Finally, the IPO will fuel a third TLR8-targeting program, but not in oncology. The ADC combines the payload with a monoclonal antibody targeting ASGR1 for the treatment of chronic hepatitis B infection. It hopes to file an IND for the program, SBT8230, in the second half of 2022, according to the filing.
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Beyond hep B, Silverback is also working on treatments that “localize therapies to modulate important pathways in additional oncology and fibrosis indications,” the company said in the filing.
Silverback's 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.
The IPO comes six months after biopharma veteran Laura Shawver, Ph.D. took the company’s helm and joins an ever-growing list of biotech companies who have gone public, or sought to do so, during the COVID-19 pandemic.