Keytruda’s $25 Billion Cliff: The Size of the Problem
When Wall Street models Merck through 2030, one figure overshadows every other: $24.7 billion. That’s Keytruda’s 2023 global revenue, currently the single highest-grossing oncology drug worldwide, generating about 45% of Merck’s total sales. The U.S. composition-of-matter patent for pembrolizumab (Keytruda) clocks out in May 2028. Formulation and method-of-use patents might stretch market exclusivity for another year or two, but the countdown on the core protection has started. And Keytruda’s impact on Merck’s operating income is even more pronounced, with a gross margin above 85%. Biotech investors can only envy that.
Biosimilar entrants are inevitable. The Congressional Budget Office estimates annual U.S. biosimilar savings of $8-12 billion for all biologics losing exclusivity each year. For Keytruda, if U.S. revenue drops even 60% within three years after loss of exclusivity, that’s a $10 billion annual gap, no rounding error.
Merck’s 2024 investor deck faces the issue head-on. Strip out Keytruda and Merck’s revenue shrinks by a third. “We know what’s coming. We’re not naive,” CEO Rob Davis told analysts. It’s frank talk, but the Street remains wary. The post-patent cliff for blockbusters like AbbVie’s Humira (adalimumab) has ranged anywhere from 30% to more than 90%, shaped by biosimilar penetration, payer leverage, and pricing. Oncology’s buy-and-bill model offers a different flavor than Humira’s retail dynamic, more like what we’ve seen with Avastin and Herceptin. But honestly, the scale here is a new beast altogether.
Biosimilar Competition and Its Messy Impact on Oncology Markets
Oncology biosimilars have a precedent, but it’s anything but straightforward. Trastuzumab, rituximab, and bevacizumab saw U.S. price erosion between 35% and 60% within three years of biosimilar entry. Yet the patient split among brands and biosimilars looked jagged, not smooth. With Keytruda’s sprawl, over 30 tumor types and lines, the switch isn’t binary. Payers want savings, but oncologists’ caution with immunotherapies adds friction.
Site-of-care is a wild card. Biosimilars in oncology are reimbursed under Medicare Part B at ASP plus 6%, and PBMs (RxPBM.ai) aren’t well positioned to redirect volume. So while biosimilar uptake in oncology usually lags retail biologics, pricing pressure remains constant. Merck, in its recent 10-K, claims oncology biosimilars often retain more than half their pre-expiry revenue for two to three years, but that’s a moving target. Nobody has a perfect read on how fast adoption will happen.
Look abroad and the pressure mounts. In Europe, biosimilar penetration for rituximab and trastuzumab topped 65% within two years, net prices falling over 60%. Japan and EU markets are tricky, centralized procurement and national formularies flatten margins with ruthless efficiency. With $10.2 billion in 2023 ex-U.S. sales, erosion outside the U.S. can’t be hand-waved away.
How Merck Is Trying to Build a Bridge, And Where It’s Still Short
Merck’s main play is to grow the oncology pie before biosimilars start biting. That’s a long pipeline game, not merely launching new drugs. Keytruda’s lifecycle extension hinges on moving into earlier-stage cancers and new combinations, chemotherapy, and antibody-drug conjugates (ADCs) among them.
Consider the recent Keytruda+chemotherapy approval for early-stage triple-negative breast cancer. Leerink analysts call it a $2 billion opportunity, but that barely dents the shadow cast by core lung and melanoma sales. Merck itself sees immuno-oncology growing at a mid-single-digit CAGR through 2027. The Prometheus (anti-TL1A) and Harpoon (T cell engager) acquisitions, $1.35 billion and $1.8 billion, respectively, signal Merck’s appetite for long-dated pipeline bets, but the reality is sobering: revenue replacement at scale arrives, optimistically, after 2030.
ADCs get plenty of limelight. Merck paid Daiichi Sankyo $4 billion upfront, chasing three ADCs (up to $22 billion in biobucks). Datopotamab deruxtecan is the lead, now in late-stage trials. Maybe $5-7 billion in peak sales, assuming everything breaks Merck’s way. It’s meaningful, but we’re still staring at a $10 billion hole.
Profit Squeeze, Pricing Battles, And What’s Next on the Deal Table
Strip away the hype, and Merck’s future boils down to margin compression. Even if biosimilar erosion is a “modest” 50% by 2030, Keytruda’s gross profit pool shrinks by $10 billion or more each year. New oncology launches rarely hit old-school biotech profit rates straight out of the gate. ADCs and combo regimens often require price cuts to win access; net margins get further dented by rebates and contracting. PBM middlemen (RxPBM.ai) are squeezing buy-and-bill profits, while employer-sponsored plans (RxBenefits.ai) increasingly shift risk onto specialty pharmacies. It’s a grind.
Outside oncology, Merck’s most recent launch, Lagevrio (molnupiravir), hasn’t moved the needle, COVID demand is down, and the window for windfall profits has closed. The only real option? More acquisitions. Prometheus and Harpoon are small steps; Merck will need mid-to-late-stage assets with $2-5 billion peak sales and a shorter runway to commercial reality. Asset prices are stretching, Phase 3 oncology programs are trading at 7x forward sales, a premium untouched since the 2015-2016 deal binge. Deals may not be accretive, but the Street cares more about predictable revenues than about near-term profitability.
If history’s a guide, expect a mix of clinical bets, creative pricing, and relentless focus on international margins. No single fix. Just a $25 billion cliff, and a patchwork of partial bridges. Honestly, I wonder if even that’ll be enough. Guess we’ll see.
