Shares of Jazz Pharmaceuticals (JAZZ) and Zymeworks (ZYME) catapulted Monday after the duo unveiled positive test results for a drug that could eventually rattle a Roche (RHHBY) blockbuster, Herceptin.
The companies suggest their drug, Ziihera, could become the new “agent of choice” following a test that featured Ziihera in two different combinations in patients with a form of gastric cancer. Like Roche’s Herceptin, the drug works by targeting and blocking the HER2 protein that shows up in some forms of cancer.
“While specific data were not provided in the topline release, the trial appears to be a sweeping success, showing highly statistically significant and clinically meaningful improvements,” Leerink Partners analyst Andrew Berens said in a report.
Jazz stock surged more than 18% to 167.02, while Zymeworks stock rocketed more than 30% to 24.25.
Significant Improvements Vs. Herceptin
Jazz Pharmaceuticals and Zymeworks tested regimens using Ziihera in patients with gastroesophageal adenocarcinoma, a cancer of the glands in the junction between the esophagus and the stomach.
The companies tested Ziihera plus two forms of cancer, and Ziihera plus chemo and BeOne Medicines (ONC) ‘s Tevimbra. Tevimbra is a checkpoint inhibitor. It works by blocking a protein cancer cells use to hide from the immune system. Once revealed, the immune system can attack the cancer cells.
Both combinations led to statistically significant improvements in progression-free survival compared to the standard of care, Herceptin plus chemo. Progression-free survival, or PFS, is the length of time patients live before their cancer worsens.
The regimen using Ziihera, chemo and Tevimbra also significantly improved overall survival, or how long patients live before dying of any cause. Ziihera plus a double chemo regimen is showing a “strong trend” toward showing a statistically significant benefit on overall survival, the companies said.
Jazz Pharma’s ‘Mic Drop’
Leerink Partners analyst Marc Goodman says the test results Monday are a “mic drop” for Jazz amid its yearslong work to transition from a specialty business into a biopharma company.
“The real evolution has been the slow and steady approach to building an oncology portfolio,” he said in a report. “Zani changes everything, in our view, because now Jazz has a legitimate $1 billion-plus oncology asset that investors can ‘dream the dream’ that this could be $2 billion or even $3 billion-plus (the glass probably now becomes half full for the breast cancer opportunity) for a company with total revenues of (about) $4 billion.”
Ziihera, or zanidatamab, works by seeking out cancer cells covered in the HER2 protein. Breast cancer is a big area of opportunity for HER2-targeting drugs.
In the first half of 2026, Jazz Pharmaceuticals plans to ask the Food and Drug Administration to sign off on Ziihera for patients with previously untreated gastroesophageal adenocarcinoma.
“Given recent market worries about the potential of this trial to disappoint: this PR should be a big sigh of relief,” Evercore ISI analyst Umer Raffat said in a client note. “PR language looks strong, and results from both arms suggest we shouldn’t be worried anymore.”
Follow Allison Gatlin on X/Twitter at @AGatlin_IBD.
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