The weight-loss drug battle is expanding into more segmented fields.

 

On November 4, rumors emerged that AstraZeneca had made an acquisition offer to obesity drug developer Rhythm Pharmaceuticals worth approximately $10 billion in total.

 

The non-binding proposal was for up to $134 per share, including some milestone payments. Earlier reports said AstraZeneca had made an offer of $124 per share last month.

 

If the deal ultimately goes through, it would become one of the highest-value acquisitions in the obesity field. Rumors suggest that if this acquisition lands, the transaction would be completed through AstraZeneca's rare disease business unit Alexion.

 

AstraZeneca acquired Alexion for a total value of $39 billion in 2021, making a major push into rare diseases. Currently, neither AstraZeneca nor Rhythm has responded to the acquisition rumors.

 

At present, the "duopoly" of Eli Lilly and Novo Nordisk seems impregnable. But interestingly, Rhythm's core pipeline completely avoids head-on competition with tirzepatide and semaglutide, instead heading toward a segmented market that GLP-1 currently does not cover.

 

Chapter 1: Rhythm Takes an Unconventional Path

 

Rhythm was founded in 2008, incubated by investment firm MPM Capital. The two co-founders, Bart Henderson and Liz Stoner, were Entrepreneur-in-Residence and Managing Director at MPM, respectively. Rhythm initially had two core assets, RM-131 (for diabetic gastroparesis, with some pain-related side effects) and RM-493 (for obesity and diabetes), both licensed from Ipsen. Later, RM-131 did not progress well and was divested by Rhythm. RM-493 ultimately "bore fruit" and received FDA marketing approval.

 

RM-493 is a melanocortin 4 receptor (MC4R) agonist (setmelanotide). In 2020, the FDA approved it for monogenic obesity caused by specific genetic defects (such as POMC, PCSK1, LEPR deficiency), under the brand name IMCIVREE. In 2022, its indication was expanded to obesity associated with Bardet-Biedl syndrome (BBS). In March 2026, the FDA again approved a new indication for the treatment of patients with acquired hypothalamic obesity (HO).

 

This is a completely different R&D pathway from GLP-1.

 

The hypothalamus is a key center for regulating appetite and energy balance in the human body. When tumors, surgery, or other factors cause hypothalamic damage, patients may experience continuous, rapid weight gain, potentially developing severe obesity.

 

The problem for these patients is not just eating too much, but that the physiological mechanisms regulating hunger and energy expenditure have become abnormal.

 

MC4R is precisely a key receptor in this regulatory pathway. IMCIVREE helps restore partial appetite regulation function by activating MC4R, thereby improving patients' weight status.

 

In contrast, GLP-1 drugs primarily act through gut hormone-related pathways. For patients with defects in specific neural pathways or genes, traditional weight-loss treatments may not address their core problem.

 

This also determines the market characteristics of MC4R drugs: relatively limited patient numbers, but clear disease mechanisms, highly concentrated clinical needs, and a lack of effective treatment options.

 

For AstraZeneca, Rhythm's most valuable aspect is first and foremost that it has already established a commercial first-mover advantage in this market.

 

Rhythm's third-quarter financial report shows that the company's global net product sales reached $92.1 million, up 29% quarter-over-quarter; the number of patients who obtained reimbursement and received treatment increased 20% quarter-over-quarter. Among this, the U.S. market contributed $67.5 million. Acquired hypothalamic obesity became an important growth driver, accounting for over 90% of the U.S. market's incremental demand quarter-over-quarter.

 

Rhythm management previously stated that the company has identified approximately 2,000 confirmed or suspected HO patients in the U.S., with an estimated total potential patient population approaching 10,000. Wall Street analysts believe this indication could form a market exceeding $1 billion in the future.

 

Commercialization of rare disease drugs is not simply about selling drugs to hospitals. Patient identification, genetic testing, disease diagnosis, physician education, and insurance reimbursement — every step has barriers.

 

Especially for diseases like HO, patients are often scattered across different medical institutions, making diagnosis and treatment somewhat difficult. Whoever first establishes a patient identification and commercialization system has the opportunity to control the market entry point.

 

Of course, Rhythm is not without concerns. In March 2026, the company announced results from the Phase III EMANATE trial, in which all four independent sub-studies evaluating setmelanotide for MC4R pathway-related genetic diseases failed to meet their primary endpoints. Post-hoc analysis observed positive signals only in two subgroups: SRC1 (NCOA1) variants and POMC/PCSK1 variants.

 

This means IMCIVREE's further expansion in the original genetic obesity field is constrained.

 

But Rhythm has not stopped — it has placed its next-stage hopes on a second MC4R drug, the oral small molecule bivamelagon licensed from LG Chem.

 

Phase II data announced last year showed that patients treated with bivamelagon experienced an average BMI reduction of 9.3%, versus 2.2% in the placebo group. The company plans to initiate its Phase III pivotal study for HO before the end of 2026, and to initiate a study for Prader-Willi syndrome (PWS) in 2027.

 

The significance of this drug is that it attempts to further expand MC4R therapy from the existing injectable to oral administration.

 

In January 2024, Rhythm reached a global licensing agreement with LG Chem, obtaining global exclusive development and commercialization rights to bivamelagon. Under the original agreement, Rhythm paid a total of $80 million in cash and $20 million worth of Rhythm common stock, and agreed to pay up to $205 million in potential regulatory and sales milestone payments, plus low-to-mid single-digit sales royalties calculated by the number of approved indications.

 

On November 3, Rhythm and LG Chem restructured the licensing agreement. Rhythm will pay LG Chem an additional total of $350 million in four installments, and the original tiered royalty structure based on the number of indications was eliminated, replaced by a fixed 1% royalty on global net sales of Rhythm's entire MC4R product portfolio. Additionally, the agreement added a new milestone of up to $200 million, triggered when the MC4R product portfolio's annual global net sales reach $3 billion.

 

At the same time, Rhythm also obtained a $750 million term loan from KKR's HealthCare Royalty and Blackstone, of which $500 million has been committed, providing funding support for subsequent R&D and commercialization.

 

Therefore, if AstraZeneca acquires Rhythm, what it buys is not just one IMCIVREE, but an asset portfolio that has already established commercialization, has a clear patient population, and is extending toward next-generation oral MC4R drugs.

More importantly, although this market is niche, it is not without competition.

 

Chapter 2: MC4R Is Ushering in the Next Round of Competition

 

The success of IMCIVREE has actually opened the door to MC4R drug development. But first-mover advantage does not mean one can rest easy. Existing therapies still have two prominent clinical issues: gastrointestinal side effects and skin pigmentation.

 

Among them, skin pigmentation is believed to be related to unintended activation of melanocortin 1 receptor (MC1R) by the drug.

 

Therefore, the core direction of next-generation MC4R drug development is already relatively clear: while retaining MC4R agonist activity, improve selectivity for MC1R, minimize off-target effects, and improve patients' long-term medication tolerability.

 

Palatin Technologies and Superluminal Medicines are two representatives in this direction.

 

Palatin's pipeline includes three complementary MC4R programs: the non-lipidated peptide PL-1000, the lipidated peptide PL-2000, and the oral small molecule PL7737.

 

Among them, Palatin plans to initiate Phase I single-ascending-dose and multiple-ascending-dose trials for PL-2000 in the first half of 2027, with preliminary safety and pharmacokinetic data planned for release in the second half of the same year; the Phase I IND application for PL7737 is expected to initiate in the second half of 2027, with data to be announced in the first half of 2028.

 

Additionally, Palatin is advancing clinical trials of the MC4R agonist bremelanotide in combination with tirzepatide. Phase II studies showed that after 8 weeks of treatment, the combination group lost 4.4% body weight, versus 1.6% in the control group.

 

This study provides a new way of thinking — MC4R and GLP-1 do not necessarily have to compete; they may also form combination treatment regimens through different mechanisms.

 

Another company, Superluminal Medicines, focuses on an AI-assisted GPCR drug discovery platform. Its current core pipeline is a selective, biased MC4R agonist, planned for the treatment of rare genetic obesity and hypothalamic obesity.

However, what is truly noteworthy about Superluminal is its backers.

 

In September 2024, Superluminal completed a $120 million Series A financing led by RA Capital Management, with Eli Lilly appearing in the investor list as a participant. And one easily overlooked detail is that Superluminal is headquartered in Eli Lilly's incubator space in Boston.

 

In August 2025, Superluminal reached a collaboration with Eli Lilly to jointly advance small-molecule therapies targeting undisclosed GPCR targets related to cardiovascular metabolic diseases and obesity, with the deal valued at up to $1.3 billion.

 

In September 2026, Superluminal completed a $60 million Series B financing, with Eli Lilly continuing to participate as an existing investor.

 

From equity investment to R&D collaboration to continued participation in subsequent financing, Eli Lilly is clearly not just focused on a single MC4R candidate drug, but also laying out broader GPCR drug discovery capabilities. This also shows that Eli Lilly has long been watching the rare genetic obesity field.

 

However, the differences in the current competitive echelon must be recognized: Rhythm has an already-marketed product and real sales revenue, and bivamelagon has entered late-stage clinical development; Palatin's and Superluminal's next-generation assets are mostly still in preclinical or early stages.

 

This precisely constitutes Rhythm's scarcity. For a multinational pharmaceutical company hoping to quickly enter the rare disease obesity field, acquisition is undoubtedly more cost-effective than starting from scratch.

 

Chapter 3: AstraZeneca's Weight-Loss Map

 

If Rhythm is placed within AstraZeneca's entire weight-loss pipeline, the strategic significance of this potential acquisition becomes clearer. Over the past few years, AstraZeneca has been continuously replenishing its obesity R&D assets. Its strategy is not to bet on just one mechanism, but to build a product portfolio covering different administration routes, mechanisms of action, and patient populations through internal R&D, external licensing, and potential acquisitions.

 

In the mainstream obesity market, AstraZeneca first bet on oral GLP-1.

 

The core asset Elecoglipron is a once-daily oral small-molecule GLP-1 receptor agonist, originally developed by Sciwind Biosciences. In 2023, AstraZeneca acquired rights outside Greater China for a transaction value of up to over $2 billion.

 

The VISTA study showed that adult patients with obesity or overweight and at least one comorbidity achieved an average weight reduction of 11.8% after 36 weeks of treatment with elecoglipron (75 mg), without reaching a plateau, versus an average weight reduction of 0.3% in the placebo group. In addition, multiple exploratory analyses of cardiometabolic risk factors showed clinically meaningful improvements with elecoglipron, including significant reductions in blood pressure and C-reactive protein (a marker of systemic inflammation) levels.

 

Another study, SOLSTICE, showed that adult patients with type 2 diabetes treated with elecoglipron (75 mg) experienced an average HbA1c reduction of 1.9% from baseline at week 26, versus 0.2% in the placebo group. Additionally, the elecoglipron group achieved an average weight reduction of 7.7%, versus 1.7% in the placebo group.

 

Based on these results, AstraZeneca initiated multiple Phase III studies in 2026, including a "head-to-head" comparison with semaglutide.

 

Oral administration is an important selling point of Elecoglipron, but AstraZeneca is clearly not satisfied with that alone.

 

In January this year, AstraZeneca also reached a strategic collaboration with CSPC Pharmaceutical Group with a potential total value of up to $18.5 billion, with an upfront payment of $1.2 billion.

 

The core of the deal is CSPC's once-monthly injectable weight management product portfolio, including the long-acting GLP-1R/GIPR agonist SYH2082, which has entered Phase I, and multiple preclinical assets. These programs will be developed based on CSPC's AI-driven peptide drug discovery platform and its proprietary LiquidGel once-monthly dosing platform technology.

 

At the same time, AstraZeneca is also laying out non-GLP-1 mechanisms.

 

AZD6234 is a once-weekly injectable selective amylin receptor agonist, currently in Phase III; AZD1043 is an ActRII antibody drug, primarily aimed at addressing the muscle loss associated with GLP-1 drug weight loss, currently in Phase I studies.

 

From these assets, it can be seen that AstraZeneca's layout is no longer limited to traditional GLP-1: oral small molecules address dosing convenience, once-monthly long-acting formulations explore new dosing cycles, and amylin and glucagon-related mechanisms provide possibilities for combination therapy.

 

And Rhythm's MC4R fills in another piece of the puzzle — rare obesity targeting specific neural pathways and genetic defects.

 

This is also one of the differences between AstraZeneca's layout and those of Eli Lilly and Novo Nordisk.

 

Eli Lilly and Novo Nordisk have already established massive sales scale and commercialization advantages in the mainstream GLP-1 market. If latecomers rely only on a similar weight-loss drug, it will be difficult to shake the existing landscape in the short term.

Oral, long-acting, combination therapy, and mechanisms beyond GLP-1 are all becoming new battlegrounds.

 

AstraZeneca is trying to capture all these directions simultaneously. Rhythm, this potential $10 billion deal, may be the most differentiated piece among them.

 

— In Conclusion —

 

The weight-loss business is dazzlingly lively.

 

Pfizer spent heavily to grab Metsera last year, and now its pipeline has been cut down to a single surviving asset. MNCs are scrambling for targets, platforms, and dosing cycles while also having to gamble on clinical trials, regulation, and commercialization. It seems like opportunities are everywhere, but in reality, risks lurk at every step.

 

The more blazing the fire, the more vigilance is needed: not every sky-high acquisition will get the ending it hopes for.

 

On November 27–28, 2026, the 17th Taizhou Medical Expo, hosted by Taizhou Medical City Guotai Exhibition Co., Ltd. and organized by Tongxieyi, will be held at the China Medical City Exhibition Center.

Among the events, the "Peptide Drug Innovation — Technological Breakthroughs and Industrialization Implementation" special session will conduct in-depth exchanges around peptide CRDMO full-chain services, high-throughput screening, new synthesis technologies and process innovation, active drug discovery, and globalization challenges.

 

References:

1. Rhythm doubles down on LG obesity license, raising payout to as much as $855M; FiercePharma

2. $10 Billion! AstraZeneca Plans to Acquire Obesity Drug Company Rhythm; Yidu Pharma

3. Rhythm obesity drug wins broader use from FDA; BioPharma Dive