PTX-299

Pinetree Therapeutics is on the cusp of closing a $47 million Series B financing, with the goal of invigorating its pipeline following a deal with AstraZeneca last year. Pinetree’s raise is currently in progress and expected to close soon, according to a company spokesperson. The financing will be led by a number of South Korean investment firms, including DSC Investment, Widwin and STIC Ventures. The cash is set to go toward getting its lead cancer programs into the clinic and advancing other parts of its preclinical portfolio. AstraZeneca and Pinetree signed their up to $500 million deal in July 2024, with Pinetree getting $45 million in upfront and near-term payments. Pinetree’s chief scientific officer Steve Gillies told Endpoints News that even though the program in the AstraZeneca deal is essentially being handed off, it represents the potential of Pinetree’s platform of protein degraders. The drug, called PTX-299, is an EGFR inhibitor that targets all EGFR rather than specific mutations. That’s different from approved EGFR inhibitors like AstraZeneca’s Tagrisso that only go after one mutation or another. The theory is that by degrading EGFR instead of inhibiting its receptors, PTX-299 can help ward off the resistance that patients eventually develop to this older class of drugs. “As you can imagine, [approved EGFR inhibitors] can work very potently in the beginning. But then after a long period of time, if [the cell] gains another mutation, then the drug stops working,” Gillies said. “Our molecule goes inside of the cell into a little vesicle called a lysosome, where it gets degraded and turned into amino acids.” Pinetree is handling PTX-299 through the IND package, after which AstraZeneca will have full control of development. But the deal and Series B are prompting the Cambridge, MA-based startup to move forward with its other protein degraders, potentially for other collaborations. Pinetree could also develop some of the programs on its own, Gillies added. Most of those decisions are still being sorted out, but Pinetree is “casting a big net,” Gillies said. “It’s certainly easy to spend money once you start manufacturing these things,” he said. “We’ll have no problem spending the money.” Pinetree researchers are also investigating ways that the degraders can be used in antibody-drug conjugate formulations. The key is finding the right balance of degrader to get into the cells in order to have a safe and effective result, Gillies said. That will likely involve using a stable linker rather than one that can unbind more easily. Once the raise is completed, Pinetree’s runway is expected to last into the third quarter of 2028.