In the U.S. healthcare system, access matters more than approval. A drug can clear regulators and still fail commercially if it cannot pass through the tightly controlled formularies run by pharmacy benefit managers. This month, one South Korean pharmaceutical company crossed that threshold in one of the most closely guarded corners of the American drug market.
Celltrion has secured preferred formulary status for its denosumab biosimilar, Stoboclo, at CVS Caremark, one of the three largest pharmacy benefit managers in the U.S. Patient reimbursement for the drug will begin April 1, a step that effectively determines whether the product will be prescribed at scale across CVS-managed health plans.
The decision carries particular weight because CVS Caremark removed the originator biologics Prolia and Xgeva from its formulary at the same time. In a system where out-of-pocket costs strongly shape prescribing behavior, that exclusion is likely to push physicians and patients toward the lower-cost biosimilar, regardless of brand familiarity.
For Celltrion, the listing marks a strategic breakthrough rather than a single-product win. With Stoboclo’s inclusion, the company now has preferred status at CVS Caremark for both of its denosumab biosimilars, placing a Korean drugmaker directly into a reimbursement channel that governs prescriptions for tens of millions of Americans. Such access is difficult even for large U.S. and European pharmaceutical companies to secure.
The move follows a similar outcome for Osenvelt, another Celltrion biosimilar used in oncology, which CVS Caremark had previously designated as the only reimbursed biosimilar in its category. That decision gave Celltrion an exclusive cost advantage within CVS-managed plans, signaling that the PBM was willing to concentrate volume behind a foreign supplier if pricing and supply conditions were met.
Because CVS Caremark operates within CVS Health, whose footprint spans insurance, retail pharmacies and clinical services, the implications extend beyond a single formulary. Preferred placement can smooth access across affiliated insurers and care networks, amplifying the commercial impact for a company that remains little known to U.S. patients.
Celltrion’s denosumab products are now preferred across two of the three largest U.S. PBMs, as well as another top-five PBM, giving the company access to a majority of the commercial reimbursement market within seven months of launch. That pace reflects an ability to navigate the opaque pricing, contracting and rebate structures that define the U.S. drug system.
The episode illustrates how a Korean pharmaceutical company is no longer competing at the margins of the American market, but inside its most restrictive mechanisms. In U.S. healthcare, the real contest is not approval, but access. Celltrion has now secured both.
