Amgen, newer rivals could threaten Novo Nordisk and Eli Lilly's weight loss drug dominance 

Novo Nordisk and Eli Lilly have long dominated the rapidly growing weight loss drug market, but their duopoly is closer than ever to facing a threat from a new rival. 

Amgen is among the leaders of a pack of drugmakers racing to join the market with their own weight loss treatments. As the company proceeds with the trials needed to bring its experimental obesity injection to the market in the coming years, it could see a few advantages.

Amgen's drug, MariTide, is taken less frequently than Novo Nordisk's Wegovy and Eli Lilly's Zepbound, and may cause longer-lasting weight loss than the market leaders' injections. Amgen, one of the nation's biggest pharmaceutical companies, can also produce drugs at scale – a huge edge over smaller biotech companies that lack a large manufacturing footprint. 

"There are a number of others trying to break into [the market] both small and large, but when I step back, I do think that Amgen has a real shot at being disruptive and challenging Eli Lilly and Novo," William Blair & Company analyst Matt Phipps told CNBC. 

Amgen has seen its shares pop 12% since CEO Bob Bradway on Thursday said he was "very encouraged" by an ongoing mid-stage study on MariTide. But it isn't the only company with a chance to upend the market.

Other companies — like Viking Therapeutics, Altimmune, Structure Therapeutics, AstraZeneca and partners Boehringer Ingelheim and Zealand Pharma — are among those that are making progress on their own treatments. Novo Nordisk and Eli Lilly are also working on new weight loss drugs.

"I don't know if I'm ready to pick another clear winner yet based on the data we have," Phipps said.

The competition for a slice of the weight loss market has only grown more fierce in recent months. Still, despite intermittent supply shortages and limited insurance coverage, demand for Wegovy and Zepbound isn't expected to slow down anytime soon. That leaves room for new entrants in a segment expected to grow to $100 billion by the end of the decade.

While Amgen is in a strong position, it will take years for MariTide to reach patients. The company has not provided an estimated launch date for its obesity injection. In a research note published Thursday, JPMorgan analyst Chris Schott estimated it will hit the market in 2028. 

Amgen is testing out a once-a-month or even less frequent basis for its drug, which would be more convenient than the weekly medicines on the market. Several drugmakers are developing weekly injections or daily pills, but some haven't ruled out testing less frequent dosing for their drugs. 

MariTide showed sustained weight loss after a single injection or multiple shots during a phase one trial, which allowed for less frequent doses of the drug, according to the study authors. They added that the company's drug can also stick around in the body for much longer than current therapies.

Phipps said he's confident that patients can take MariTide even less frequently, such as once a quarter, to maintain the weight loss they saw after starting the drug. That could make it easier for Amgen to manufacture enough supply – and avoid an issue that has been plaguing Novo Nordisk and Eli Lilly.

Amgen is already starting to expand manufacturing capacity for MariTide, executives said during an earnings call on May 2.

Less frequent doses of MariTide may also cause fewer side effects than other weight loss treatments, Phipps noted. Many patients stop taking existing drugs due to nausea and vomiting.

MariTide causes some of those same side effects, but Phipps said a monthly or quarterly injection of the drug would lead to fewer days of feeling sick compared with a weekly dose. He added that fewer doses could help patients stick to the treatment and maintain weight loss.

"Even if you do have some nausea for the day, just once a quarter versus once a week I think that's huge for getting more patients to stay on," said Phipps. 

Much like Wegovy and Zepbound, Amgen's treatment activates a gut hormone receptor called GLP-1 to help regulate a person's appetite. 

But while Zepbound activates a second appetite-suppressing hormone receptor called GIP, Amgen's drug blocks it. Wegovy does not target GIP, which as a receptor may also improve how the body breaks down sugar and fat.

While Amgen's progress has excited Wall Street and sent its stock climbing, other companies are also moving toward putting a product on the market. Here is where those other drugs stand.

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

They include a weekly injection from Novo Nordisk for diabetes and obesity called CagriSema. That drug combines semaglutide, the active ingredient in Wegovy, along with an experimental drug called cagrilintide. 

CagriSema helped diabetes patients who were overweight or obese lose 15.6% of their weight after 32 weeks in a mid-stage trial. Novo Nordisk is studying CagriSema in six late-stage clinical trials and could release data from a 68-week study in obese patients later this year.

Meanwhile, Eli Lilly is studying an experimental drug called retatrutide in a late-stage trial. That treatment helped patients lose up to 24% of their weight after almost a year in a mid-stage trial, which set a new bar for weight loss.

Retatrutide mimics three different hunger-regulating hormones: GLP-1, GIP and glucagon. That combination appears to be even more effective at curbing a person's appetite.

Eli Lilly is also developing an oral drug called orforglipron, which targets GLP-1. The company is slated to release late-stage trial data on the pill and retatrutide in 2025. 

Among other potential entrants, Boehringer Ingelheim and Danish biotech firm Zealand Pharma are developing a weekly weight loss injection. The experimental drug targets GLP-1 to suppress appetite and glucagon to increase energy expenditure. 

Boehringer Ingelheim in August said it was moving the drug, called survodutide, into a late-stage study. A mid-stage trial found patients who are overweight or have obesity lost up to 19% of their weight after 46 weeks of treatment with the drug.

In February, the companies also posted positive mid-stage trial data on survodutide in patients with a severe form of liver disease.

Boehringer Ingelheim hopes survodutide will launch as a treatment for obesity or liver disease in 2027 or 2028, as long as trial data is favorable, according to a Reuters interview.

AstraZeneca is also developing a daily obesity pill, called ECC5004, under a partnership it inked with Chinese biotech company Eccogene in November. 

AstraZeneca executives have said the pill is rapidly absorbed and doesn't stay in the stomach long, which could reduce side effects relative to existing treatments. Executives have also said that patients can take the pill alone or in combination with its other oral drugs, such as the diabetes drug Farxiga, to treat obesity and related health issues.

But the drug, which targets GLP-1, is years away from entering the market. The company has completed a phase one trial in patients with diabetes and plans to present the data at a medical conference later this year, executives said during an earnings call in April.

Also in an early-stage trial is AstraZeneca's experimental obesity drug AZD6234, which targets another gut hormone called amylin. The company hopes it can combine AZD6234 with its oral GLP-1 to help patients achieve greater weight loss than with existing drugs, AstraZeneca CEO Pascal Soriot said in November.

Meanwhile, investors are eager to see new data on Pfizer's once-daily obesity pill around the middle of the year, which will determine the company's fate in the weight loss drug market. The company scrapped the twice-a-day version of that pill, danuglipron, in December after patients had a difficult time tolerating it in a trial. 

Pfizer could have another chance to enter the market if it acquires a smaller obesity drugmaker. But for now, a deal appears unlikely as the company works to rebound from the decline of its Covid business last year.

"As it relates to bolt-on acquisitions, in the near term you would not expect us to do much there," Pfizer Chief Financial Officer David Denton said during an earnings call on May 1.

Beyond those major pharmaceutical companies, Viking Therapeutics, Altimmune and Structure Therapeutics have drawn immense attention to their respective weight loss drug pipelines. The trio has far fewer resources and less manufacturing capacity than Amgen or Pfizer, but that could change if they get scooped up by a large drugmaker. 

Viking Therapeutics in March released initial data from a mid-stage trial on its experimental injection, which targets GLP-1 and GIP. Those who received weekly doses of the treatment lost up to 13.1% of their weight compared with patients who received a placebo after 13 weeks. 

Viking will likely conduct another phase two trial that could last between six and nine months, the company's CEO Brian Lian said during an investor call in March. Viking's treatment likely won't reach the market until 2029 or later, Jefferies analyst Akash Tewari wrote in a note that same month.

Also in March, Viking said it plans to start a phase two trial on an oral version of its drug after it showed positive results in a small study.

Structure Therapeutics is also developing an oral GLP-1 for obesity and diabetes. But it missed Wall Street's expectations for weight loss in a mid-stage trial in December.

The pill helped obese patients lose roughly 5% of their weight compared with those who received a placebo after eight weeks.

Structure said it expects full 12-week results on patients with obesity in the second quarter of this year. The company plans to start a larger mid-stage study in the second half of this year and a late-stage trial in 2026. 

Altimmune is developing a weekly obesity injection called pemvidutide, which targets GLP-1 and glucagon.

In November, Altimmune released mid-stage trial data showing that its drug caused 15.6% weight loss on average after 48 weeks. The company also announced additional data from that study in March showing that its injection minimized the loss of muscle mass, a negative side effect of existing weight loss injections. 

Altimmune will meet with the Food and Drug Administration in the second half of the year to chart a path forward for the injection.

Correction: This article has been updated to reflect the correct spelling of Bob Bradway's name.