To amend title XVIII of the Social Security Act to require PDP sponsors of a prescription drug plan under part D of the Medicare program that use a formulary to include certain generic drugs and biosimilar biological products on such formulary, and for other purposes.

HR8143 was introduced on March 27, 2026 by Rep. Matsui (D-CA) with two bipartisan cosponsors (Miller-Meeks, Auchincloss) and referred to the Energy and Commerce and Ways and Means Committees. At early stage, the bill faces significant hurdles but has clear bipartisan sponsorship. The bill amends the Social Security Act to require Medicare Part D PDP sponsors that use formularies to include each covered generic drug (at WAC below reference) and at least two biosimilars (at WAC below reference) in a preferred position starting January 2027. It also prohibits imposing more restrictive utilization management (prior auth, step therapy) on these generics/biosimilars versus their reference brand products. The money trail: This bill does not authorize or appropriate any federal funds. Its mechanism is a regulatory mandate on private insurers/PBMs administering Medicare Part D. The economic transfer flows from brand manufacturers and PBMs to generic/biosimilar manufacturers via forced formulary access. The estimated total market impact is in the billions annually when fully implemented, redistributing existing Part D spending from higher-cost brands to lower-cost alternatives. Structural winners: Viatris ($VTRS) and Teva ($TEVA) as two of the largest generic/biosimilar manufacturers by US prescription volume benefit from guaranteed preferred access on ~50M Part D lives. Biosimilar leaders in the oncology and immunology space (Amgen's biosim portfolio, $AMGN) have moderate exposure but Amgen's larger branded portfolio offsets this benefit. Structural losers: PBMs ($CVS, $CI) lose rebate arbitrage revenue; Brand manufacturers ($PFE, $MRK, $JNJ) lose Part D formulary access for products facing generic/biosimilar competition. Real market data shows generic/biosimilar pure plays already reflecting this thesis: $VTRS up +13.56% and $TEVA up +10.02% over the trailing 30 days, while $MRK (-8.02%), $JNJ (-5.27%), and $PFE (-2.07%) show declines in the same period. PBMs show mixed signals: $CVS (+15.55% 30-day) and $CI (+8.76%) have rallied from lower bases, possibly reflecting broader market rotation and repricing of separate risk factors. Timeline: Bill is early stage. Next steps: committee hearings and markups in Energy and Commerce and Ways and Means. If it advances in 2026, it could be folded into must-pass healthcare legislation or a year-end omnibus. The January 2027 effective date is aggressive for a bill still in committee. Probability of passage in current form this session: moderate-to-low, but the policy signal — mandating generic preferred placement — is a growing bipartisan trend.