Sutro Biopharma is at it again—on the heels of an $85 million private round, the oncology player has filed to raise up to $75 million in its IPO. The funding will support the clinical development of two antibody-drug conjugates being developed for blood cancers and solid tumors.
South San Francisco-based Sutro has a clutch of pipeline hopefuls, including bispecific antibodies and cytokine derivatives in addition to antibody-drug conjugates (ADCs). While it’s partnering on some of those programs with Merck, Celgene and EMD Serono, its IPO haul will be used primarily to advance a pair of in-house ADCs, the company said in its S-1, filed Wednesday. The IPO funds will also bankroll technology development, including manufacturing, Sutro said.
Sutro’s STRO-001 is in phase 1 for lymphoma and multiple myeloma, while STRO-002 is scheduled to enter the clinic for ovarian and endometrial cancers by early 2019.
Its in-house assets are based on its ExpressCF+ platform, comprising cell-free protein synthesis and site-specific conjugation platforms. They allow Sutro to quickly evaluate a variety of protein structures and manufacture a "highly optimized single molecular species" instead of the "imprecisely conjugated antibodies" made using conventional cell-based approaches, the company says.
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Sutro raised $85.4 million in its series E round in late July, five years after it picked up $26 million in its series D.
There are already a few ADCs on the market—Roche's HER2-targeting breast cancer drug Kadcyla, for one—and there are several more in development.
Novo Holdings recently invested $20 million in Switzerland's NBE Therapeutics, which will use the cash to start testing an anti-RO1 ADC in patients with solid tumors. But chasing ADCs isn’t going well for everyone—in April, AbbVie ended an early-stage trial for its ADC designed for solid tumors and Swiss biotech ADC Therapeutics dumped an asset targeting HER2-positive breast cancers because of toxicity issues. However, ADCT did say its decision to pull the program would not affect its other ADC assets, which are in early clinical development for a range of solid and blood cancers.