Eli Lilly and Company (LLY) shares moved lower, falling roughly 2% after the latest weekly prescription snapshot showed uneven performance across its GLP-1 products.
For the week of April 17, 2026, IQVIA data cited by Morgan Stanley recorded Mounjaro at about 758,400 total prescriptions and 367,900 new prescriptions, up from 749,500 total and 361,700 new prescriptions the prior week. Zepbound registered roughly 615,300 total prescriptions and 350,600 new prescriptions for the same week, versus 632,500 total and 346,400 new prescriptions in the preceding week.
When combined with Trulicity and Foundayo, the week’s total prescriptions for Mounjaro, Trulicity, Zepbound, and Foundayo reached 1,503,100, a decrease of 0.3% from 1,508,000 the previous week. Narrowing the view to the newer GLP-1 entrants, the Mounjaro, Zepbound, and Foundayo grouping totaled 1,377,400 prescriptions, down 0.3% from 1,381,000 the week before.
Despite the slight week-over-week shifts in volumes, Eli Lilly’s GLP-1 franchise - comprised of Mounjaro, Trulicity, and Zepbound - held approximately 59% of weekly new prescription market share, unchanged from the prior week. The wider GLP-1 category continued to expand, growing about 32% year-over-year according to the same data set.
Foundayo, which received regulatory approval on April 1, 2026 and began commercial availability on April 9, 2026, recorded around 3,700 total and new prescriptions in its second week on the market. By comparison, oral Wegovy registered approximately 18,400 total and new prescriptions during its second week following a January 5, 2026 launch.
Analysts at Morgan Stanley highlighted the importance of the two new product cycles for Lilly - the diabetes launch of Mounjaro and the obesity indication for Zepbound - as they monitor how those introductions shape category expansion and share dynamics. The firm also indicated potential upside, writing, "We see ~6% upside to '26 M+Z ests," referencing combined 2026 estimates for Mounjaro and Zepbound.
Market reaction to the weekly script report translated into a modest pullback in Eli Lilly shares despite the sustained market share position and the broader category's year-over-year growth. The data underscore that while demand for GLP-1 therapies remains elevated, short-term week-to-week variations and initial launch volumes for new therapies remain focal points for investors and analysts tracking commercial momentum.
Contextual note: The figures cited above are drawn from IQVIA prescription data as reported by Morgan Stanley for the week of April 17, 2026, and reflect the early commercial performance of Foundayo following its April launch.