Novo Nordisk (NVO -0.32%) and Eli Lilly (LLY -1.38%) are the top two companies in the weight loss market right now. They are both raking in billions in revenue from their glucagon-like peptide-1 (GLP-1) drugs. But given how lucrative the market is -- one estimate says it will be worth $100 billion by 2030 -- you can be sure that there will be a lot of competition.

In fact, several small, up-and-coming healthcare companies are developing GLP-1 weight loss drugs in the hopes of striking it big in the anti-obesity drug market. Yet, the immediate and bigger concern for Novo Nordisk and Eli Lilly may be competition from larger and more established healthcare companies. These are rivals with significant resources and manufacturing capabilities that can not only bring a product to the market, but can do so quickly. One potential rival looming over the horizon that Novo Nordisk and Eli Lilly investors should keep a close eye on is Roche (RHHBY 0.20%).

A multi-pronged strategy

The Swiss pharma giant is developing multiple GLP-1 weight loss drugs that have been showing promise in early-stage trials.

One is CT-388, which is a weekly injectable, similar to the approved GLP-1 treatments on the market today. In an early-stage trial, it has helped people lose nearly 19% of their body weight after a period of 24 weeks. That's right up there with Eli Lilly's Zepbound, which has helped people achieve 21% weight loss -- but over a much longer time frame of 72 weeks. Wegovy, Novo Nordisk's approved weight loss treatment, has averaged 15% weight loss after 68 weeks. It's still early on, but if CT-388 can maintain these types of numbers without any concerning side effects, it has the potential to be a genuine threat in the GLP-1 weight loss market.

Another drug to watch for is CT-996, which is a daily pill. In a four-week period of taking the pill, patients achieved a placebo-adjusted weight loss of 6.1%, on average. The drug won't enter phase 2 trials until next year, but an effective weight loss pill could appeal to a wider range of patients and have more growth potential in the long run.

The candidates could enter the market earlier than anticipated

Previously, Roche was a bit of a dark horse in this market, as it wasn't expecting to come out with an obesity treatment until the next decade. But the company is reportedly looking to accelerate the development of these drugs, and it could potentially have a weight loss drug on the market by as early as 2028.

While that's not imminent, it's a sign that the healthcare giant is taking the market seriously. The longer that drugs such as Zepbound and Wegovy dominate the market, the more recognizable their names become, the more comfortable patients are with taking them, and the more difficult it may become for new drugs to take away market share.

Roche has a market cap of more than $250 billion, is a big name in healthcare, and will be a formidable rival for Novo Nordisk and Eli Lilly to worry about. While it may still be years before Roche enters the GLP-1 weight loss market, investors shouldn't underestimate its potential.

Could Roche stock be an underrated buy?

Roche trades at a much more attractive earnings multiple than Eli Lilly and Novo Nordisk, which have a lot of GLP-1-driven growth expectations priced into their current valuations. Roche trades at 21 times its trailing earnings, while Novo Nordisk is at a multiple of 44 and Eli Lilly is well over 100.

While there could be a lot of upside potential in Roche's stock if it comes to market with a successful GLP-1 drug, it's still far too early to tell how probable that will be. Every drugmaker would love to be able to tap into those opportunities, but that doesn't mean they'll eventually compete with Zepbound and Wegovy. The bar has been set high by those drugs, and that's why investors are paying significant premiums for shares of Novo Nordisk and Eli Lilly.

Still, Roche is a stock worth watching. But if you want exposure to the GLP-1 weight loss market now, you may be better off going with Novo Nordisk or Eli Lilly. They already have approved, established drugs on the market that have been doing exceptionally well, and there's still plenty of room for their sales to rise higher.