The “diet drug duos” Novo Nordisk (NVO.US) and LLY.US (LLY.US) have long dominated the rapidly growing diet pills market, but the duopoly is now closer than ever to facing the threat of new rivals. Amgen (AMGN.US), for example, is one of the market leaders with many pharmaceutical companies competing to launch their own weight loss treatments. As the company undergoes the trials needed to bring experimental bariatric injections to market in the next few years, it may see some advantages.

Amgen's drug MariTide is used less frequently than Novo Nordisk's WegoVy and Eli Lilly's ZepBound, and may take longer to lose weight than market leaders' injections. However, as one of the largest pharmaceutical companies in the US, Amgen can also produce drugs on a large scale — this is a huge advantage over smaller biotech companies, and the “diet drug duo” lacks large-scale production bases.

William Blair & Company analyst Matt Phipps said in an interview: “There are many other companies, big and small, trying to break into [the market], but when I look back, I really think Amgen has an opportunity to disruptively challenge Eli, Novo, and Nordisk. Based on the data we have, I don't know if I'm ready to pick another clear winner.”

Amgen CEO Bob Bradway said on Thursday that he was “very encouraged” by MariTide's ongoing mid-term study, and the company's stock price has risen 12% since then. But it's not the only company that has the chance to disrupt the market. Other companies, such as Viking Therapeutics (VKTX.US), Altimmune (ALT.US), GPCR.US (GPCR.US), AstraZeneca (AZN.US) and their partners Boehringer Ingelheim and Zealand Pharma, are also making progress on their own treatments. Novo Nordisk and Eli Lilly are also rushing to develop new weight loss drugs.

Competition in the weight loss market has intensified in recent months. However, despite intermittent supply shortages and limited insurance coverage, demand for Wegovy and Zepbound is not expected to slow anytime soon. This has left room for new entrants, and the market is expected to grow to $100 billion by the end of this decade. Despite Amgen's strong position, MariTide will take years to reach patients. The company has yet to provide an estimated launch date for its weight loss injections. J.P. Morgan analyst Chris Schott estimated in a research report released on Thursday that it will go public in 2028.

Novo Nordisk and Eli Lilly's new drugs are coming to market

Novo Nordisk and Eli Lilly are developing new medicines for weight loss and diabetes that may improve their current treatments and enter the market sooner than MariTide and other experimental drugs.

This includes Novo Nordisk's weekly injections of a drug called Cagrisema for diabetic and obese patients. This drug combines cimaglutide (Wegovy's active ingredient) with an experimental drug called cagrilintide. In an interim trial, CagriseMA helped overweight or obese diabetics lose 15.6% of their body weight after 32 weeks. Novo Nordisk is studying CagrisEMA in six advanced clinical trials and may release data from a 68-week study of obese patients later this year.

Meanwhile, Eli Lilly is studying an experimental drug called ritaglutide, which is already in the advanced stages of testing. After almost a year of mid-term trials, this treatment helped patients lose up to 24% of their body weight, setting a new standard for weight loss. Ritrutide mimics three different hunger-regulating hormones: GLP-1, GIP, and glucagon. This combination appears to be more effective at suppressing a person's appetite.

Eli Lilly is also developing an oral medication called orforglipron, which targets GLP-1. The company plans to release late-stage trial data for the drug and rituglutide in 2025.

Amgen seems to have a competitive advantage

Amgen is testing monthly or even less frequent medication treatments, which will be more convenient than weekly medications on the market. Several pharmaceutical companies are developing weekly or daily injections, but some don't rule out testing their medications less frequently.

The study's authors said that in the first phase of the trial, MariTide showed sustained weight loss after a single or multiple injections, which reduced the dosage of the drug. They added that the company's drugs also stay in the body for much longer than current treatments.

Phipps notes that he believes patients can take MariTide less often, for example once a quarter, to maintain the weight loss they saw after they started taking the medication. This may make it easier for Amgen to produce sufficient supply and avoid the problems that have always plagued Novo Nord and Eli Lilly. Amgen executives said during the May 2 earnings call that the company has begun to expand MariTide's production capacity.

Phipps notes that smaller doses of MariTide may also cause fewer side effects compared to other weight loss treatments. Many patients stop taking existing medications due to nausea and vomiting. Although MariTide has some of the same side effects, Phipps says injecting the drug monthly or quarterly will reduce the number of days of nausea compared to taking it once a week. He added that reducing doses can help patients stick to treatment and maintain weight loss.

“Even if you do have some nausea, once a quarter instead of once a week, I think that's huge for more patients to stick around,” Phipps said.

Like Wegovy and Zepbound, Amgen's treatment activates an intestinal hormone receptor called GLP-1 to help regulate a person's appetite. However, Zepbound activates a second appetite suppressing hormone receptor called GIP, and Amgen's medication avoids this receptor. Wegovy doesn't target GIP, and GIP as a receptor can also improve the way the body breaks down sugar and fat.

While Amgen's progress has excited Wall Street and boosted its share price, other companies are also trying to bring their products to market.

AstraZeneca and Pfizer (PFE.US) are developing competitive products

In November of last year, AstraZeneca reached a cooperation agreement with Chinese biotech company Eccogene (Eccogene) to develop a daily diet pill called ECC5004. AstraZeneca executives say the tablets absorb quickly and don't stay in the stomach for long, which may reduce side effects compared to existing treatments. Executives also said that patients can take the drug alone or in combination with other oral medications (such as the diabetes drug Farxiga) to treat obesity and related health problems.

However, it will take several years for this drug against GLP-1 to enter the market. The company's executives said during the April earnings call that the company has completed the first phase of the trial for diabetics and plans to release the relevant data at a medical conference later this year.

AstraZeneca's experimental weight loss drug, AZD6234, is also in early trials. The drug targets another intestinal hormone called amylin. AstraZeneca CEO Pascal Sooriot said in November that the company hopes to use AZD6234 in combination with GLP-1 oral medication to help patients achieve greater weight loss results than existing drugs.

Meanwhile, investors are eager to see Pfizer's new daily diet pill data in the middle of the year, which will determine the company's fate in the diet pills market. In December of last year, the company cancelled a twice-a-day trial of the drug danuglipron because in one trial, it was difficult for patients to tolerate the drug.

If Pfizer buys a smaller obesity pharmaceutical company, it could have another chance to enter the market. But for now, as the company struggles to bounce back from last year's COVID-19 business decline, reaching an agreement seems unlikely. David Denton, chief financial officer at Pfizer, said during the May 1 earnings call: “We won't be doing much in the short term due to the reinforcement of the acquisition involved.”

Potential competition is fierce, and the future is bright for smaller biotech companies

Among other potential competitors, Boehringer Ingelheim and Danish biotech company Zealand Pharma are developing weekly weight loss injections. The experimental drug targets GLP-1 to suppress appetite and target glucagon to increase energy consumption.

Boehringer Ingelheim said in August of this year that the drug called survodutide is being advanced to a later stage of research. An interim trial found that overweight or obese patients lost 19% of their weight after taking the drug for 46 weeks. In February of this year, the two companies also released mid-term trial data on the survival rate of patients with severe liver disease. According to the interview, Boehringer Ingelheim hopes that as long as the trial data is favorable, survodutide will be marketed as a treatment for obesity or liver disease in 2027 or 2028.

In addition to these major pharmaceutical companies, Viking Therapeutics, Altimmune, and Structure Therapeutics have also attracted attention due to their respective weight loss drug pipelines. Compared to Amgen or Pfizer, these three companies have far fewer resources and production capacity, but this could change if they were acquired by a major pharmaceutical company.

In March of this year, Viking Therapeutics released preliminary data from a mid-term trial of an experimental injectable for GLP-1 and GiP. Compared to patients treated with placebo after 13 weeks, patients receiving weekly doses lost 13.1% of their body weight.

Viking Therapeutics CEO Brian Lian said during an investor conference call in March that the company may conduct another phase II trial, which could last 6 to 9 months. Jefferies analyst Akash Tewari wrote in a report in the same month that the company's treatment plan may not reach the market until 2029 or later. Also in March, Viking Therapeutics said it plans to begin phase two trials of oral medications after showing positive results in a small study.

Structure Therapeutics is also developing an oral GLP-1 for obesity and diabetes. But in a mid-term trial in December last year, it failed to meet Wall Street's expectations for weight loss. After eight weeks, the drug helped obese patients lose about 5% of their weight compared to those taking a placebo. The company said it expects the full results of the 12-week treatment for obese patients in the second quarter of this year. The company plans to begin large-scale mid-term research in the second half of this year and conduct advanced trials in 2026.

Altimmune is developing a weekly bariatric injection called pemvidutide that targets GLP-1 and glucagon.

Last November, Altimmune released mid-term trial data showing that its drug lost an average weight of 15.6% after 48 weeks. The company also published additional data from the study in March, showing that its injections minimized loss of muscle mass, a negative side effect of existing weight loss injections. Altimmune will meet with the US Food and Drug Administration (FDA) in the second half of this year to set the future direction for this injectable.