Plexxikon vets kick off new drug discovery outfit — with old assets and new target

Daiichi Sankyo shut down its South San Francisco subsidiary Plexxikon earlier this year. Now a new startup is looking to forge its own path — with 10 Plexxikon veterans, five assets from the now-defunct biotech and a focus around a new target.

Opna Bio, led by ex-Plexxikon CEO Gideon Bollag, announced its emergence from stealth this morning — combined with a $38 million Series A round.

Plexxikon, bought out by Daiichi in 2011 for $935 million, was shut down earlier this year as the Japanese pharma planned to streamline efforts to further R&D into Enhertu and two other ADCs. The company, which was founded more than two decades ago, pushed two cancer therapies all the way past FDA: the Roche-partnered Zelboraf for melanoma, and Turalio for tenosynovial giant cell tumors in 2019.

Douglas Hanahan

Opna Bio, according to Bollag, was founded back in 2019 — and there is more connection to Bola’s previous company, Onyx Pharmaceuticals, than Plexxikon. Douglas Hanahan, one of Opna’s co-founders and head of the biotech’s scientific advisory board, knew Bollag from his time at Onyx.

“And really independently of Plexxikon, at the very beginning of the pandemic, when I was still CEO at Plexxikon, Doug called and had this news story and asked if I would be interested in it, and looked into it. It was very exciting,” Bollag said.

What that story was — and what distinguishes Opna from other biotechs — is a protein called fragile X messenger ribonucleoprotein, or FMRP, and using it in oncology drug development. Hanahan and his lab published a paper last week in Science about the protein being expressed in cancer and are hypothesizing that it is involved in helping tumor cells evade the immune system.

The protein, encoded by the FMR1 gene, has normally been associated with neurons, Bollag tells Endpoints News. However, as Hanahan and lab pointed out, increased levels of FMRP were noted in certain cancers, including pancreatic, colon, breast, prostate and lung cancer.

That discovery led Hanahan’s lab to try to find out why cancer cells are expressing it — since normally they should not be able to, Bollag pointed out. And as it turns out, FMRP is a master regulator of translation and mRNA stability — and that plays a role in cancer evading detection by the immune system. Additionally, that might lend a hand to the treatment of certain cancers that are immune to checkpoint inhibitors.

Bollag added that the whole idea is that if that protein can be blocked by a small molecule, then the host immune system should be much more able to go after and destroy the tumor.

So far, candidate screening and selection are still ongoing.

On top of that effort, Opna Bio said it acquired five oncology candidates from Plexxikon — including two clinical stage programs. One, BET inhibitor OPN-2853, is in a Phase I/II trial for myelofibrosis, and the other (OPN-7486) is a CSF1 inhibitor planned to start Phase II sometime next year. The remaining three candidates are still in preclinical development.

In the meantime, the 15-person biotech says it has a goal to find a partner, and that emerging out of stealth will enable the company to have more discussions with more possible interested parties. And speaking of the $38 million the company raised via Series A, it will last Opna well in 2024.

Investors in that round included Longitude Capital, Northpond Ventures and Menlo Ventures.

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