California’s governor has vetoed a bill that would have required pharmacists to notify doctors when substituting biosimilar therapies for branded biologics, calling it “premature” and adding to a growing list of states that have opposed similar measures.

The California bill would have made it a misdemeanor for pharmacists to substitute a biosimilar for a prescribed biologic if a doctor forbade it or the biosimilar exceeded the cost of the brand-name drug. Given California’s size and national influence, the bill’s fate may influence the national fight over how and when biosimilars will be substituted, choices that fall under state law.

Biosimilars are similar, though not exact copies of original biologic therapies. Owing to development, testing, and marketing costs lower than the branded biologics with which they compete, their use in California alone could potentially lead to as much as $27.6 billion in savings over the ten-year period between 2014 through 2024, according to an analysis by Express Scripts, a pharmacy benefits manager that opposed the bill.

Had the bill passed, it would have impeded access to biosimilars, says Ralph Neas, president and CEO of the Generic Pharmaceutical Association. He says the bill was designed to drive profits at companies with biologics threatened by biosimilars, such as Amgen and Genentech, which backed the California bill and support other state laws like it.

The California’s Public Employees’ Retirement System, the state’s largest retirement and health benefits group, and other large purchasers opposed the bill as well. They warned that the notification requirement “would cast doubt on the safety and desirability of more cost-effective alternatives to (branded) biologics,” wrote Governor Jerry Brown in his veto message. Since the FDA has yet to determine what standards will be required for biosimilars to meet the high standards of “interchangeability,” he wrote, requiring doctors to be notified of substitutions “strikes me as premature.”

The U.S. Food and Drug Administration is still developing its approval pathway for biosimilars, a process that is momentarily stalled due to the federal government shutdown. Nonetheless, the Biotechnology Industry Organization is working to lay the groundwork for state laws to protect patient safety and blunt the impact of biosimilar competition on its members.

Legislation that would limit substitution has passed in Oregon, Utah, and Virginia and is pending in Massachusetts and Pennsylvania, according to information from the Generic Pharmaceutical Association.

In a statement after Brown’s veto, BIO said it was disappointed and that providing notice to patients and physicians would “allow everyone involved the opportunity to discuss past treatment experiences so that any possible unexpected issues can be better understood and avoided.”