Viking Therapeutics (VKTX -41.32%) stock collapsed in morning trading Tuesday, down more than 40% after reporting mixed results for its GLP-1 weight loss pill VK2735. As Viking shares plummet, however, one rival is having a better day.

Novo Nordisk (NVO 0.80%) stock is up 2.2% through 10:30 a.m. ET on Viking's bad news.

GLP-1 weight loss drug in a syringe.

Image source: Getty Images.

Why Viking's bad news is good news for Novo Nordisk

In its morning press release, Viking emphasized that its "Phase 2 VENTURE-Oral Dosing Trial of VK2735 [in] Tablet Formulation" showed the GLP-1 drug to be "safe and well-tolerated," and noted average weight loss was 12.2% across 13 weeks of once-daily pill-popping.

This all sounds like good news for Viking, but with a couple caveats: First, 20% of participants dropped out of the study citing uncomfortable side effects. And second, weight loss rival Eli Lilly (LLY 0.82%) recently reported a study of its own GLP-1 pill that did nearly as well as Viking's -- 11.5% weight loss.

And Novo Nordisk? Studies show its GLP-1 pill -- Wegovy in pill form -- helped patients lose 12% to 13%!

Is Novo Nordisk stock a buy?

Now factor in all the other good news Novo Nordisk has been announcing this week -- a new partnership with GoodRX to sell Ozempic and Wegovy at discount prices, a cash discount offer on Ozempic when ordered directly from Novo Nordisk, and FDA approval to use Wegovy to treat liver disease in adults. And factor in the fact that Novo Nordisk stock costs less than 14 times trailing earnings today, versus more than 45 times earnings for Eli Lilly (while unprofitable Viking is currently earning nothing at all).

Add all that up, and it's pretty clear that Novo Nordisk stock is the best value stock in GLP-1 drugs today.