Spread Margins Go Public: $9B in Gross-to-Net Arbitrage Cut
The landscape shifted dramatically with last year’s Q2 CMS filings, where, for the first time, major PBMs revealed spread-based margins in Medicare Part D topping $9 billion a year. Real industry insiders never doubted such margins existed; anyone who’s attended a manufacturer-PBM negotiation knew the spread was baked in. But this time, line-item disclosure wasn’t voluntary. CMS mandated it. By April 2025, plan sponsors could finally see exactly how much PBMs kept as the delta between drugmaker rebates and sponsor pass-throughs, product by product, and in total.
The fallout was immediate. Regional Blues plans, emboldened by fresh data showing AWP-to-net spreads sometimes soared past 25% for preferred brands, pushed to reprice 2025 contracts midstream. UnitedRx’s Medicare business led the way, clawing back $400 million in previously hidden “retained savings” within just six months. That move set the tone for the 2026 renewal cycle. Transparency around rebates shifted from a compliance box-tick to a real lever for plan sponsors with the analytics to use it. By the start of 2026, public PBM filings showed average spread-based margins in Part D dropping from 14% to just 6%, a roughly $9 billion annual rebate windfall redirected out of PBM coffers.
Manufacturers, for their part, suddenly had access to credible, product-level net pricing benchmarks, no more reliance on PBM quarterly summaries or “trust us” attestation letters. The data’s already impacting benchmarks at RxInfo.ai, where analysts see the gross-to-net gap shrinking fast for diabetes, anticoagulant, and respiratory drugs. Game changed.
Are Opaque PBM Contracts Finally Over? Rebate Pass-Through Takes Center Stage
During the early 2020s, the big three PBMs, CVS Caremark, Express Scripts, Optum, routinely structured deals to keep a slice of manufacturer rebates under the guise of “administrative fees.” These fees were slippery, often buried in contract addenda labeled as “value-based” or “performance” holdbacks. But the 2025 CMS rules forced sunlight onto every dollar. High-volume specialty drug pass-through rates, once glossed over, were now revealed: in some cases, just 76% made it to the plan.
By 2026, plan sponsors walked into negotiations with a completely new hand of cards. Several Fortune 100 employers, brandishing CMS rebate audits, began to insist on full rebate pass-through and audit rights, no more black boxes. PBMs adjusted their business models fast, transitioning to per-script admin fees and fixed-service charges to make up for lost spread revenue. On an earnings call, Express Scripts conceded that over 40% of its new commercial contracts now operate on a “100% rebate pass-through plus admin fee” model, up from under 10% the prior year.
Not every plan sponsor has capitalized. Mid-market groups lacking actuarial muscle remain stuck in legacy spread contracts. In contrast, national health systems and jumbo employers have wielded CMS disclosures to demand transparency, even monthly NDC-9 level reporting. Manufacturers are recalibrating “gross-to-net” assumptions in forecasts, with PBM analytics teams at RxPBM.ai watching the trend line for rebate pass-through accelerate.
Manufacturers Shift Strategy: List Prices Flatten Under the Microscope
CMS transparency had an almost immediate effect on manufacturer pricing. 2025 saw an uptick in “rebate minimization” strategies: companies like Novo Nordisk and Gilead started closing up the list-net gap, which had long been disguised by complex rebate layers. By mid-2026, the top 20 branded drugs dropped their gross-to-net discounts from 54% to 41%. PBMs simply couldn’t shield bloated list prices behind rebate walls any longer.
The shift is even starker for specialty and pricey generics. For Part D, manufacturers are now offering front-loaded price cuts instead of back-end rebates. With sponsors viewing every dollar, any “shadow margin” held by PBMs triggers a contract challenge. Pfizer’s 2026 pipeline in oncology and rare disease stands out: launch gross-to-net discounts down 20-25% against 2023 benchmarks, and lower initial WACs, data visible at RxNews.ai.
What’s new? Pharmacies and specialty distributors now have a fighting chance to model reimbursement (and risk) with real data, not PBM self-reporting. That’s changing cash flow modeling. Larger wholesalers are tapping into CMS datasets, recalibrating risk, especially for high-cost specialty launches, finally, no more guesswork dictated by the PBM’s black box. Maybe it took too long, but the shift feels fundamental.
Negotiation Tables in 2026: Data Now Holds the Upper Hand
Anyone who’s ever wrangled over rebate guarantees knows the real sticking points were always hidden somewhere in the appendix. But post-2025 CMS rules, every side comes to the table armed with hard, public data. PBMs can’t hide off-invoice deals with manufacturers and show sponsors a different net. Now, NDC-level, auditable reporting is the standard for any plan with real leverage, and even mid-size groups are outsourcing analytics to rebuild PBM financial flows from CMS filings.
This shift is upending PBM value propositions. No more promises of magical net cost savings built on “proprietary” rebate pools. Now, big PBMs lead with speed of adjudication, operational capability, and patient services. Transparent PBMs like Navitus and Capital Rx are seizing share in the union and public sector worlds by delivering pass-through guarantees tied back to CMS-reported data. A national employer survey found 58% demand quarterly rebate reporting based on CMS definitions, up from just 27% a year ago.
From the manufacturer vantage point, CMS transparency is being used to “truth test” PBM claims and model access scenarios more precisely. Picture a PBM telling a manufacturer it passes through 99% of GLP-1 rebates, now, both the manufacturer and sponsor can check that claim against CMS data and call out discrepancies in real time. Result: contract windows are tightening, “spread” carve-outs are rarer, and up-front price competition is replacing rebate games. Fewer “true-up” disputes too, down 20% in 2026 as contracts lean on independent rebate verification. Makes you wonder how much time, and money, was wasted on arguing over black-box numbers for a decade.
Still, let’s not kid ourselves. The biggest payers and manufacturers (those who can afford to mine, parse, and exploit the new datasets) now hold the most leverage. CMS transparency didn’t kill the PBM business, but it pushed all the margins into the open. In 2026, if you’re negotiating pharmacy contracts without benchmarking against these public disclosures, you’re already a step behind.
