What happened

Shares of Seattle Genetics (NASDAQ:SGEN) are up 12% at 12:05 p.m. EDT after the biotech presented a pair of positive clinical trial results at the 2019 European Society for Medical Oncology (ESMO) Congress.

So what

In a phase 2 clinical trial testing Seattle Genetics' tucatinib with Roche's Herceptin in patients with a specific type of late-stage colorectal cancer, over half of the 23 patients responded to the therapy. The combination delayed the progression of the tumor and/or death by 8.1 months. Patients lived for a median of 18.7 months.

There wasn't a control arm to compare the data with, but these are heavily treated patients who have already failed two other approved treatments, so a 52.2% response rate is pretty impressive.

Doctor showing a report to a man in a hospital bed

Image source: Getty Images.

Seattle Genetics also presented initial data from a phase 1 clinical trial, dubbed EV-103, testing its enfortumab vedotin (EV) with Merck's (NYSE:MRK) Keytruda in patients with previously untreated, locally advanced, or metastatic urothelial cancer who can't take a chemotherapy called cisplatin. The response rate for the combination was 71% for the 45 patients, with 13% having a complete response and the other 58% having a partial response.

There wasn't a control arm to compare the data with in this study, either, but a phase 2 study that Merck used to get Keytruda approved for urothelial cancer patients who can't take cisplatin showed 29% of patients responded to the drug. Even in patients with high expression of PD-L1, the pathway that Keytruda targets, the response rate was only 47%, substantially below the 71% response rate for the combination.

Now what

Both drugs are already in late-stage testing -- EV is already under Food and Drug Administration review -- but the data at ESMO will help the biotech expand the potential market for both drugs.

EV is under FDA review for patients with late-stage urothelial cancer who have already received a PD-1/L1 inhibitor, such as Keytruda, so moving it into the first-line setting would greatly increase the number of urothelial cancer patients eligible to take EV.

Tucatinib is in a late-stage trial called Her2climb in patients with metastatic breast cancer, so the data in colorectal cancer offers a new opportunity to expand into an additional tumor type, while also giving investors additional confidence that Her2climb will be positive.