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CytomX Therapeutics, Inc.
CytomX Therapeutics develops "masked" cancer drugs that stay inactive until they reach a tumor, aiming to hit cancer harder while sparing healthy tissue.
CytomX Therapeutics is a clinical-stage biotech company building a new kind of cancer medicine. Its core idea is the "Probody" — an antibody drug wrapped in a mask that keeps it switched off while it travels through the bloodstream. The mask only comes off when the drug reaches the tumor, where enzymes that are common around cancer cells snip it away. The result: a drug that hits the tumor hard but mostly leaves healthy tissue alone, which could mean fewer of the nasty side effects that normally cap how much cancer drug a patient can take.
The reason this matters is that many powerful cancer targets also sit on healthy tissue, so ordinary antibodies cause collateral damage. CytomX's bet is that masking the drug widens the therapeutic window — the gap between "helps the patient" and "poisons the patient." The company's lead program, a Probody version of an approved cancer drug, is being tested in a Phase 3 trial in a type of skin cancer, making it one of the more advanced bets in the field. It has also struck partnerships with larger drugmakers such as Amgen, Bristol Myers Squibb, Regeneron, and Moderna, which pay CytomX upfront and milestone money to use its masking technology on their own programs. Here is the catch, and it is a big one. CytomX has no approved product and no product revenue. Almost all of its money comes from those collaboration deals and from investors. It spends heavily on research and clinical trials, burns cash every quarter, and has repeatedly restructured to stretch its runway. Clinical-stage biotech is a brutal business: a single failed trial can wipe out most of a company's value overnight, and CytomX has had its share of pipeline setbacks. Its survival depends on trial data, partner payments, and its ability to raise more money.
So the simple version: CytomX is a science-heavy, pre-revenue company selling a clever idea — drugs that wake up only at the tumor — and it lives or dies on whether that idea works in patients and whether big partners keep paying to use it.
Saved answer · last researched 14 Nov 2026