Booted by Big Pharma, Turnstone asks public investors to fund early-phase cell therapy trials

Turnstone Biologics is about to show whether public investors have regained their appetite for high-risk, high-reward programs. Having lost deals with AbbVie and Takeda, and shrunk its head count, the biotech has filed for an IPO to fund early-phase development of tumor-infiltrating lymphocytes (TILs).

San Diego-based Turnstone put itself on the map throughout 2016 and 2017, when it raised a $41 million series B round, was name-checked on the Fierce 15 and landed a deal with AbbVie. The early progress was built on evidence that Turnstone could realize the long-unfulfilled promise of oncolytic viruses. Takeda joined the party in 2019, inking a $900 million deal to co-develop Turnstone’s lead oncolytic virus. 

Today, AbbVie and Takeda are gone, and Turnstone, having bought a TIL platform, has pivoted away from oncolytic viruses. The new-look biotech is focused on delivering phase 1 data on its lead asset TIDAL-01 in indications including breast and colorectal cancers. Initial clinical updates from the two trials are due in mid-2024.

Turnstone is yet to set a target for the size of its IPO but is looking to generate enough money to fund phase 1 work on TIDAL-01, plus work to move another TIL into the clinic and run combination trials with viral immunotherapies. 

The IPO paperwork reveals details of the changes that have happened at Turnstone. AbbVie, having paid $90 million to work with Turnstone in 2017, terminated its alliance with the biotech in 2019. Turnstone landed the Takeda deal months after losing the other agreement, only for the Japanese drugmaker to follow AbbVie out the door. Takeda dropped its development deal in 2022 and a discovery pact in 2023. 

Months after receiving notice from Takeda, Turnstone reduced its workforce and subleased its space in New York to consolidate operations at its headquarters in San Diego. The biotech ended March with 108 full-time employees and $64 million in the bank. 

Turnstone is one of a small band of biotechs seeking to go public. Another potential member of the IPO class of 2023, Intensity Therapeutics, made minor changes to its paperwork late last week. The number of shares offered, 3.25 million, and target range, $4 to $5, are unchanged from the previous version. The changes include the revelation that Intensity’s landlord is terminating the lease on its facility.