California Supreme Court Weighs Drugmakers' Duty to Develop Safer Medicines

The California Supreme Court heard arguments Wednesday in a case that could decide whether drugmakers have a legal duty not just to sell an approved medicine, but to keep developing a safer one once the first product is already on the market.

The dispute, docketed as S283862 and known as the Gilead Tenofovir Cases, involves about 24,000 HIV patients. At issue is whether Gilead Sciences can be held liable for continuing to sell tenofovir disoproxil fumarate, or TDF, after the company later developed tenofovir alafenamide fumarate, or TAF, which plaintiffs say caused fewer kidney and bone problems. The court heard the case in San Francisco’s Earl Warren Building, with oral argument set for 9:00 a.m. and public attendance and live streaming available.

The timeline is central to the fight. Gilead’s first TDF-based medicines won FDA approval in 2001. The company says it stopped TAF development in 2004, arguing that the safety and effectiveness difference did not justify more spending. The FDA later approved Gilead’s TAF-based regimen Genvoya on November 5, 2015, and Descovy’s label lists an initial U.S. approval in 2015. Gilead says it redirected its efforts toward single-tablet, once-daily HIV combinations built around TDF, which it says helped replace more complicated multi-pill regimens.

That history now feeds a broader legal question. The California Court of Appeal ruled on January 9, 2024, that the plaintiffs could proceed on negligence claims, saying a manufacturer’s duty of reasonable care can extend beyond avoiding defective products. It rejected fraudulent concealment claims because TAF was not available as an alternative treatment at the relevant time. If the Supreme Court endorses that view, drugmakers could face future liability not only for selling unsafe medicines, but for not moving fast enough on reformulations that may reduce harm.

Gilead says that logic would go too far. In public filings, the company warned that such a ruling would “weaponize innovation itself.” It also says both TDF- and TAF-containing medicines remain FDA-approved and are listed in U.S. HIV treatment guidelines, underscoring that the case is about alleged timing and commercialization decisions, not whether the drugs are medically useful today.

The ripple effects could extend well beyond HIV treatment. More than 70 entities filed amicus briefs or similar filings opposing a duty-to-innovate theory, warning that it could raise drug prices, shift research priorities, and pressure companies to spend more aggressively on every possible improvement. For patients, especially those who depend on lifelong antiviral therapy, the case asks whether the law should reward faster access to safer reformulations or preserve the current line between approved medicine and unfinished innovation.