Eli Lilly (LLY -4.58%) stock has had plenty of good trading sessions over the past year or so, but Monday's sure wasn't among them. The storied pharmaceutical company's shares lost nearly 5% of their value during the big market sell-off that day, and it wasn't only because of the general gloom. That drop compared rather unfavorably to the relatively light 2.7% swoon of the S&P 500 (^GSPC -2.70%).

No, no, Novo

That negative investor reaction was directed at companies involved in the white-hot weight loss drug segment of the market (Eli Lilly is the pharmaceutical giant behind a popular one, Zepbound).

That morning, Wegovy maker Novo Nordisk announced the latest clinical trial results for an advanced obesity drug it's developing, CagriSema. Participants treated with CagriSema achieved weight loss of 15.7% after the 68-week duration of the trial. The drug seemed to have demonstrated a safe, well-tolerated profile.

Although Novo Nordisk described this result as "superior," it was well short of the 25% weight loss that the company had anticipated. Investor hopes were similarly high, so it's little wonder those folks were bearish on Novo Nordisk. They also punished fellow obesity drug developers like Eli Lilly in a sympathy sell-off.

An easily discouraged market

I don't think investors in either company should give up because of these results. The weight loss drug segment is still quite new, and there will be many fits and starts by developers.

Zeroing in on Eli Lilly, the company is already well established with Zepbound, which should continue to sell briskly as the world waits for a more powerful and efficacious obesity drug to hit the market. Besides, the American pharmaceutical king has many other products currently on pharmacy shelves, and a wide and active pipeline.