This is the weight-loss drug company. Mounjaro and Zepbound, two brands of the same drug, are the best-selling medicine on Earth, and Lilly just launched the first pill version, Foundayo. The business is extraordinary: revenue grew 48% last quarter, and the next drug in line, retatrutide, produced the biggest weight-loss numbers ever seen in a trial.
The catch is the price of the stock. At ~$1,273 you pay about 43 times last year's earnings for a future that is already in the consensus forecast. Great company, full price. The interesting question is not whether Lilly wins. It is what you should pay for the win.
The base case lands just under the 12% growth bar at today's price, and even the bull case does not reach 30%. The same base case clears 12% from any entry below about $1,200. Hence watching, and patient.
Mounjaro (diabetes) and Zepbound (obesity) are the same drug, tirzepatide, wearing two labels. Together they did $27.7 billion in the first half of 2026, about 65% of everything Lilly sells, growing at 91% and 46%. The patent on the molecule runs to 2036 in the US, with follow-on patents listed into the 2040s. That is the moat and the concentration risk in a single fact.
Injections cap the market at people willing to inject themselves every week. Foundayo, approved in April 2026, is a once-a-day pill with no food or fasting rules, starting at $149 a month for self-pay patients. It is less powerful than the shots, about 12% of body weight in trials, and that is fine: its job is to turn a specialist product into a primary-care habit for the largest patient pool in medicine.
Retatrutide adds a third hormone target and produced 28.3% average weight loss in its big Phase 3 trial, the largest number the field has recorded. Lilly plans to file it with the FDA in early 2027, for obesity, sleep apnea, and knee pain. The watch items are tolerability: a tingling side effect called dysesthesia, and higher dropout rates at the top dose. If it clears those, it becomes the premium tier, sold by the same company that sells you the standard tier.
Last quarter Lilly sold 60% more product at 13% lower realized prices. That is the new shape of this market: Medicare pays $245 a month under the deal struck with the White House in late 2025, China listed Mounjaro nationally and the local price fell sharply, and every future competitor launch negotiates against Lilly's price. The growth is real. It just has to outrun a price that mostly moves one way.
Novo Nordisk's next drug, CagriSema, failed to match tirzepatide in a head-to-head trial that Novo ran itself. Novo's pill is on the market and fighting Foundayo now. Amgen's MariTide, dosed monthly instead of weekly, is the threat with a real difference, and its big trials read out in 2027. Pfizer bought its way in for about $10 billion and aims at 2028. Nobody has to beat Lilly outright to hurt the stock. Trimming its price or its share at the edges is enough.
Lilly built the largest supercomputer owned by a drug company, 1,016 NVIDIA chips, live since February 2026, opened a $1 billion joint AI lab with NVIDIA, and runs TuneLab, a platform where more than 135 smaller biotech companies use Lilly's drug-discovery models and feed improvements back. Our base case gives this exactly zero revenue. If AI-discovered drugs start coming out of it later this decade, that is upside nobody is paying us to forecast.
At about 43 times trailing earnings, the stock needs the good decade to happen on schedule. Analysts, who like the stock almost unanimously, put the average target only about 5% above the price. Our base case gets roughly 11% a year to 2031: strong compounding, and still a notch below the 12% bar, because the entry multiple collects its share first. The fix is not a better story. It is a lower price, and prices like that usually arrive on a scare, not on good news.
About 65% of revenue is tirzepatide. A safety problem, a payer revolt, or a genuinely better rival drug is not a bad quarter. It is the thesis. Generic drug makers already filed legal challenges to the patents in July 2026, years ahead of the 2036 expiry.
Government deals cap the US price, foreign health systems pay far less, and each new competitor uses price to buy share. The base case assumes erosion of about 3% a year. If it runs at 8%, the base case breaks.
Nothing has to go wrong with the business for this stock to fall 25%. One ordinary earnings miss at 43 times earnings does it. The next print is October 29, five days after this note.
Lilly spent about $13.3 billion on acquisitions and drug rights in the first half of 2026, and took a $3.03 per share charge in a single quarter for bought research. Debt is up to about $54.9 billion. If the bought pipeline disappoints, the one-off charges become the story.
Retatrutide's dropout rates and tingling side effect, plus the pill's mid-tier efficacy, are reminders that these drugs ask a lot of patients, for years. Real-world persistence, not trial results, decides how big the treated pool actually gets.