The lucrative market for weight loss drugs won’t stay a duopoly forever. With billions at stake, that’s pretty much been a guarantee facing the current market leaders, Eli Lilly and Novo Nordisk , from the start. But the reality of the coming competition has grown more tangible after recent announcements from rival drugmakers Roche and Viking Therapeutics . Both companies have made progress with experimental treatments that promise to help patients shed more pounds faster. Their updates are likely to be joined by others in the coming months even as today’s incumbents develop their own next-generation weight loss treatments. Still, the headlines have taken a toll. Over the past two weeks, Eli Lilly has lost about $123 billion in market value, logging its worst eight-day decline since the eight days ended March 23, 2020, when it fell 15%. Over the same period, Novo Nordisk shares tumbled about 10%, its worst eight days since mid-August 2022, when its stock dove 11.4%. Even with this recent pullback, both stocks have logged massive gains this year, Lilly surging 38% and Novo up nearly 23%. To be sure, part of the recent selling likely came from investors taking some profits after a long, steady run. Indeed, a similiar trend has been playing out among megacap tech stocks that have led the broader stock market’s gains this year. LLY YTD mountain Eli Lilly shares year to date. Analysts say Indianopolis-based Lilly and Denmark’s Novo have a wide enough lead in the anti-obesity category to lock in growth for a long time. UBS analyst Trung Huynh doesn’t expect competition to enter the market until around 2028. Even then, rivals will be limited to no more than 10% of the market until 2029, Huynh said. On Monday, UBS increased its forecast for the GLP-1 (glucagon-like peptide 1) market , predicting it will grow at a compound annual rate of 33% until 2029, hitting $150 billion in sales by 2029, up from a previous forecast of $125 billion. The reason for the higher estimate is the expectation that more people with obesity will seek treatment, UBS said in a research note. Other analysts have also grown more optimistic about the future of weight loss treatments. “As the clinical data around cardiovascular risk, kidney disease and other co-morbidities risk-reduction benefits build up, we think the pace of access and adoption will increase,” said Rajesh Kumar, an analyst at HSBC Global Research. Kumar said the concerns about competition are “fair,” but “too soon.” “It is true that many players are developing assets targeting obesity,” he said. “However, the time required to build out clinical data, access and manufacturing scale remains the key barrier to entry.” Meanwhile, analysts say Lilly and Novo may continue to surprise to the upside as they work to ramp up manufacturing capacity. Demand for weight loss drugs far outstrips supply. Where the competition stands Roche’s recent announcements suggest it could become the third large-cap company to enter the anti-obesity drug market. On July 17, the Swiss company disclosed that CT-996, a once daily, oral GLP-1 treatment it acquired with the purchase of Carmot Therapeutics, helped patients with obesity in a phase 1 clinical trial lose an average of 6.1% of their starting weight in four weeks. That was an impressive result. Orforglipron, a once-a-day oral GLP-1 drug that Lilly is working on, had shown a 3% weight loss at 4 weeks. Many have been hoping for an effective oral GLP-1 treatment as both Novo’s Wegovy and Lilly’s Zepbound are delivered through a once a week injection. Patients typically favor taking a pill over administering a shot, and pills tend to be less costly to manufacture. Roche will advance CT-996 to a phase 2 trial next year, while continuing to study CT-388 , which is delivered via a weekly injection. It’s also considering whether combination therapies make sense, which could broaden the market for the drugs. Roche ADRs are ahead 12.5% so far in 2024. VKTX YTD mountain Viking Therapeutics shares year to date. Viking Therapeutics surged 30% last week after revealing that VK-2735 — an injectable drug that combines two gut hormones, GLP-1 and GIP (gastric inhibitory polypeptide) — would speed directly into a phase 3 program after it met with the Food and Drug Administration. The company is also exploring whether the weight loss treatment could be given only once a month. BTIG analyst Justin Zelin said Viking appears “increasingly confident” that monthly dosing is a possibility, an achievement he believes would be “icing on the cake.” Like Lilly and Novo, Viking is also working on an oral drug, which will move to a phase 2 trial in the fourth quarter. Zelin expects more detail on the trials at the ObesityWeek conference in San Antonio in early November. He rates Viking shares a buy and has a $125 price target, slightly higher than the $114 average target on Wall Street, according to FactSet. Even with Viking’s strong rally last week, the stock has 89% upside ahead if it hits Zelin’s target. More news ahead Further advancements in the GLP-1 space are expected throughout the second half of this year, further boosting Lilly and Novo stock. Two big events on the calendar are a mid-September conference in Spain for the European Association for the Study of Diabetes and ObesityWeek two months later. HSBC’s Kumar has identified at least 125 drug pipeline candidates to treat obesity at various stages of development. The market has heard recent updates from players including Pfizer and Amgen as well as Structure Therapeutics and Altimmune . Plus, Lilly and Novo aren’t sitting still. Kumar expects a readout on Novo’s next-generation drug, CagriSema , in the fourth quarter will “de-risk Novo’s longer-term growth potential.” Below is a table of some of the clinical trials investors are anticipating news from later this year. —CNBC’s Nick Wells contributed to this report.