Treasury Buybacks Ease Yields, Moderna Surges

Treasury buybacks expanded on Aug. 19, 2026, pushing long-term Treasury yields lower and helping lift U.S. stocks, while Merck and Moderna (MRNA) reported positive Phase 3 melanoma results that buoyed healthcare names.

Treasury Expands Buybacks and Market Impact

The U.S. Treasury said it will at least double the size of its liquidity-support buyback operations for longer-dated nominal coupon securities, raising the maximum per-operation cap to at least $4 billion for the 10- to 20-year and 20- to 30-year sectors. This change will run from Sept. 9 through Nov. 4, 2026. Treasury plans to revisit buyback sizes at the Quarterly Refunding and publish an updated schedule afterward.

Secondary estimates indicate the expansion adds at least $14 billion of liquidity support this quarter, lifting maximum repurchase capacity to $83 billion over the program window. The buyback program, launched in May 2024, aims to improve liquidity in off-the-run securities within the roughly $32 trillion Treasury market.

The move followed a period when long-dated yields reached their highest levels in nearly two decades, straining trading in less frequently traded Treasuries. After the announcement, long-term yields declined sharply, and global bond yields also retreated. Market participants reduced exposure to long-dated interest-rate risk and shifted toward risk assets, lifting U.S. stocks. Treasury emphasized it does not intend to use buybacks to manage episodes of acute market stress.

Merck and Moderna Report Positive Phase 3 Melanoma Trial

Merck and Moderna issued a joint press release at 6:45 a.m. ET on Aug. 19 announcing positive topline results from the Phase 3 INTerpath-001 trial in patients with completely resected stage IIB–IV cutaneous melanoma. The trial tested intismeran autogene (V940/mRNA-4157), an individualized neoantigen mRNA therapy, combined with Keytruda (pembrolizumab) versus Keytruda alone in the adjuvant setting.

The study met its primary endpoint of recurrence-free survival (RFS) and a key secondary endpoint of distant metastasis-free survival (DMFS). The companies described these improvements as "statistically significant and clinically meaningful" compared with Keytruda alone. They characterized INTerpath-001 as the first positive Phase 3 readout for an individualized neoantigen therapy and the first for an mRNA-based cancer therapy, marking a late-stage milestone for mRNA cancer vaccine approaches.

The randomized, double-blind, placebo- and active-comparator-controlled global trial (NCT05933577) reported topline results from a pre-specified interim analysis. Detailed efficacy and safety data will be presented at an upcoming medical conference. Earlier Phase 2 data showed a roughly 49% reduction in risk of recurrence and distant metastasis for the combination versus Keytruda alone.

Market and Sector Response

Following the Treasury announcement, long-term yields declined sharply, and U.S. stock indices rose, reflecting improved risk appetite. Healthcare stocks, particularly Merck and Moderna, were notable contributors to equity gains. The combination of eased rate sensitivity from the Treasury buybacks and the positive melanoma trial created distinct catalysts that lifted healthcare names and reinforced overall risk appetite.