SACRAMENTO, Calif. — Gov. Jerry Brown on Saturday vetoed legislation that would have allowed California pharmacists to dispense substitute medications that are biologically similar to brand-name treatments.

Biological medicines, which are created from living cells rather than by mixing chemicals, have been used to treat cancer and immune-system disorders.

Those treatments are becoming a fast-growing segment of the pharmaceutical market, with manufacturers also creating medications that are similar to some biological medicines. Unlike traditional generic medications, the so-called biosimilars resemble but are not identical to the biological medication they are replicating.

In his veto message, Brown wrote that he supports allowing pharmacists to substitute potentially cheaper biosimilar medication for a brand-name treatment once these drugs are approved by the U.S. Food and Drug Administration.

However, he says the state should wait until federal regulators determine when biosimilars can be used. Brown added that a second portion of the bill, which would have required pharmacists to contact the prescribing doctor to inform which medication was dispensed, seemed premature.

He noted that doctors he spoke with would welcome the information, but that the California Public Employees' Retirement System believed that the requirement "would cast doubt on the safety and desirability of more cost-effective alternatives to biologics."