The number that frames the quarter is a tension, not a single figure. Eli Lilly's Q1 2026 quarterly report on Form 10-Q, filed April 30, 2026, states that for the quarter the volume increase was primarily driven by Zepbound and Mounjaro, while the lower realized prices were primarily driven by Zepbound.
That is the central fundamentals signal for the GLP-1 leader: tirzepatide is selling more units while capturing less per unit. The drug is the same molecule under two brands — Mounjaro in type 2 diabetes, Zepbound in obesity — and Lilly's annual filings track tirzepatide across both indications. The company's FY2025 10-K, filed February 12, 2026, lists tirzepatide (Mounjaro, Zepbound) across its cardiometabolic-health programs including heart-failure work.
On the call color the proxy adds, Lilly's 2025 proxy statement points to positive topline results from the SURMOUNT-1 Phase 3 176-week study of tirzepatide, citing a 94% reduction in the risk of developing type 2 diabetes — the kind of long-duration outcome data that supports volume expansion into prevention-adjacent populations even as net pricing compresses.
The fundamentals-first read: volume-led growth with falling realized price is a maturing-blockbuster pattern. It can still produce strong absolute growth, but it shifts the franchise's value driver from price to units and from access to manufacturing scale — and the filing names Zepbound specifically as the source of the price give-back.
The volume-versus-price language and the SURMOUNT-1 outcome above are quoted from Lilly's primary SEC filings, surfaced via EdgarBeast as a filing-evidence index — the Q1 2026 10-Q, FY2025 10-K, and 2025 DEF 14A on sec.gov.