The modern drug hunter has a curious problem. Biology has become unusually good at naming villains, yet chemistry still cannot arrest most of them. The human proteome contains roughly 20,000 proteins. Thousands are implicated in disease; approved medicines touch only a fraction. For decades the remainder acquired a theatrical label: undruggable. It sounds like a law of nature. More often, it means the customary test could not see a useful place to bind.
BridGene Biosciences exists to quarrel with that label. Founded in 2018 by mass-spectrometry veteran Ping Cao and operations leader Irene Yuan, the San Jose company built IMTAC - Isobaric Mass Tagged Affinity Characterization - to look for small-molecule interactions across many proteins at once. The essential choice was setting. Rather than isolate a purified protein on a bench and hope it keeps the shape it had in nature, BridGene puts its chemical probes into living cells.
That distinction is not laboratory décor. Some proteins present shallow pockets. Others reveal a temporary pocket only while touching another protein. Strip them from the cell and the opening may vanish. A beautifully controlled assay can therefore become a portrait of the wrong subject.
One molecule catches. Its twin cross-examines.
The neatest feature is a pair. BridGene says it has built more than 10,000 pairs of drug-like covalent small molecules. Molecule A carries an alkyne tag, a chemical handle that lets scientists capture and identify the protein it has attached to. Molecule B is the same basic compound without the tag. It competes for the same site. If the untagged molecule displaces the tagged probe, the result is stronger evidence that the interaction is real rather than sticky chemical gossip.
Covalent compounds form durable bonds, which helps faint interactions survive the journey to the mass spectrometer. BridGene also designs reactive groups for amino acids beyond the field's familiar cysteine - including lysine and tyrosine. More reactive opportunities mean more of the proteome comes into view. The corresponding danger is obvious: a molecule that binds readily must still bind selectively. Covalence is leverage, not absolution.
“We pick targets with clear biology but challenging chemistry.”Ping Cao, co-founder and CEO
A platform with two cash registers
BridGene sells discovery in two ways. For pharmaceutical companies, it runs target-focused campaigns, finds covalent hits and helps carry them into early lead development. The company says these screens can test about 5,000 compounds a month across four targets and return validated hits in four to six months. Partners obtain development and commercialization rights; BridGene receives research payments, success-based milestones and potential royalties.
Takeda supplied the first conspicuous vote of confidence in 2021 with a neurodegeneration collaboration. That work reached a preclinical milestone. In early 2025, the companies signed a broader agreement covering three immunology and neurology targets. BridGene was promised $46 million in combined upfront and possible preclinical payments, with further clinical and commercial milestones that could bring the total to roughly $770 million, plus royalties.
The conditional verbs matter. A milestone ceiling is not money in the bank. It is a map of everything that must go right. Galapagos offered a similar structure in 2024 for oncology: up to $27 million in upfront and preclinical research payments, more than $700 million in possible later milestones, and tiered royalties. These figures reveal partner appetite. They do not predict approval.
The engine has not been cheap. BridGene has raised $78.5 million across three disclosed venture rounds: a reported $12 million Series A in 2021, $38.5 million in 2022 and another $28 million in 2025. The second cash register is riskier and potentially richer: proprietary drugs. Here BridGene is the customer of its own machine. Seven pipeline projects appear in company materials, but the lead program carries most of the public weight. BGC-515 is an oral covalent inhibitor of TEAD, a transcription factor connected to the Hippo signaling pathway and the growth of some cancers.
The first thing that failed was the old picture
There is no public tale of BridGene surviving a single cinematic corporate failure. The failure that changed Cao's mind was broader and more useful: target-by-target discovery repeatedly left important disease proteins untouched. Purified-protein screens could miss native conformations; genetic insight could identify a culprit without supplying a chemical foothold. After more than two decades in biopharma, including work at Tularik and Amgen, Cao concluded that chemoproteomics and mass spectrometry could turn those blind spots into a parallel measurement problem.
The resulting TEAD program moved quickly by preclinical standards. BridGene says IMTAC identified TEAD1 as the top binding target of an early compound, and optimization produced a preclinical candidate in less than a year. Mouse xenograft data showed tumor regression. The US Phase 1 trial began dosing in June 2024 and plans to study BGC-515 in advanced solid tumors, including mesothelioma and epithelioid hemangioendothelioma.
That makes the trial more than a pipeline event. It is the first occasion on which the platform must stop grading its own homework. A binder must become a tolerable drug; exposure must reach the tumor; pathway logic must translate into benefit. The cleverness of a screen can shorten the search without shortening human biology.
What another drug hunter can steal
The copyable lesson is experimental design, not the compound library. Study a target in the setting where it performs its actual job. Build competition into the assay instead of treating validation as cleanup. Capture binding site, selectivity and structure-activity information early enough to influence chemistry. Choose targets with strong disease biology and weak conventional chemistry - “clear biology, challenging chemistry,” in Cao's phrase.
The business design is copyable too. Partner programs can pay for a discovery engine and expose it to outside scrutiny; retained programs can preserve upside. The arrangement works best when one platform genuinely repeats across targets, when partners contribute development muscle the smaller company lacks, and when internal projects are few enough to fund properly.
It works poorly when cellular binding is mistaken for therapeutic effect, when reactive chemistry creates off-target toxicity, or when the target's biology is impressive only in a model. It also falters if a small company accepts so many collaborations that its own pipeline becomes an afterthought. Speed to a hit is valuable. Speed to a medicine is a different unit.
The map gets crowded
BridGene occupies a busy corner of modern drug discovery. Frontier Medicines, Vividion, Scorpion and Terremoto pursue their own versions of previously inaccessible biology. Conventional biochemical screens, fragments and DNA-encoded libraries remain credible alternatives. BridGene's claim to distinction is the combination: paired probes, live-cell engagement, covalent chemistry across several amino-acid residues, quantitative mass spectrometry, and an engine that serves both partners and an internal pipeline.
The company presented fresh preclinical work in 2025 on a selective covalent FGFR3 inhibitor and a PAX8 binder for ovarian cancer, alongside a broader map of ligandable sites in classes such as GPCRs and phosphatases. The breadth is promising. It is also a list of future obligations. Each new target must travel the distance between a molecular encounter and a useful medicine.
BridGene has already changed one question. Instead of asking whether a protein is druggable in the abstract, it asks whether the protein has been observed in the right place, with the right chemical bait and a witness standing beside it. That is a smaller claim than conquering the undruggable proteome. It may be the more consequential one.