A small molecule walks into a cell and takes out the trash.
It is 2026, and inside a low building on Scranton Road, a robot is sorting through millions of single cells. Each one has been dosed with something new - a candidate molecule, a tweaked scaffold, a long-shot idea from a chemist on the third floor. The robot is looking for one thing: the cells where a particular protein has quietly disappeared.
That disappearing act is the entire pitch of Plexium. For a century, the playbook of small-molecule drug discovery has been to find a pocket on a target protein and jam something into it. Block. Inhibit. Antagonize. Plexium's bet is different. Don't block. Delete. Recruit the cell's own disposal machinery - the E3 ligases that normally tag worn-out proteins for destruction - and convince it to take out a protein it would otherwise leave alone.
This is targeted protein degradation, or TPD. It's the hottest field in pharma chemistry, and Plexium has spent eight years staking out a specific corner of it: monovalent direct degraders and molecular glues. The kind of small, drug-shaped molecules a pill can carry.
What changed in 2025
The last twelve months were not a victory lap. The Amgen collaboration - a deal worth up to $500 million when signed in 2022 - wound down. Layoffs followed. By summer, the company looked smaller, leaner, and arguably more interesting. In late August 2025, Plexium filed paperwork showing a fresh $60.1 million had landed. Existing investors stayed at the table. The AbbVie pact, focused on neurological diseases, kept going.
Around the same time, PLX-4545 - an oral CRBN-based molecular glue degrader of IKZF2 - finished its phase 1 study in healthy volunteers with a clean safety profile and evidence it could reprogram regulatory T cells. The next step is cancer patients.
The platform behind the molecules
Most of what Plexium does at the bench is platform work. DELTA Discovery is a proprietary ultra-high-throughput cell-based screening system. Translation: instead of testing compounds against an isolated protein in a tube, DELTA tests them inside live cells, often at a scale of millions of compounds per campaign. The advantage is obvious only in hindsight: a degrader has to enter a cell, find a ligase, recruit a target, and trigger the actual destruction. Plenty of molecules that look beautiful in a tube fail one of those steps. DELTA only counts the ones that survive all four.
That platform has powered partnerships with Amgen and AbbVie, and an internal pipeline that's now in the clinic. It is also, if you ask the venture investors who keep funding it, the moat. Pipelines change. Platforms compound.