ImmunityBio (IBRX) fell about 9% as traders continued to react to regulatory and legal overhang tied to ANKTIVA marketing. The key backdrop is an FDA Office of Prescription Drug Promotion warning letter dated March 13, 2026 focused on promotional communications the agency characterized as false or misleading, a development that triggered a sharp selloff in late March and remains a near-term sentiment drag. (ir.immunitybio.com)

On April 6, 2026, ImmunityBio filed an 8-K and issued an update saying it submitted a comprehensive response to the FDA warning letter and described corrective actions, including removing the identified podcast from its website, requesting removal from third-party platforms, and implementing enhanced compliance measures; it also said a referenced TV advertisement was never aired. Even with that response, the episode can keep pressure on the stock as investors assess reputational risk, potential commercial friction, and any constraints on future promotional efforts. (ir.immunitybio.com)

Class-action-related headlines have re-entered the tape in recent days, with filings and investor-law-firm announcements centered on the same FDA promotion dispute and the March 24, 2026 stock drop. These updates don’t typically change fundamentals on their own, but they can weigh on risk appetite and keep short-term trading choppy. (globenewswire.com)

IBRX has been carrying elevated short interest, which can magnify intraday moves when negative catalysts hit or when liquidity thins. Data for the March 31, 2026 report date shows short interest around 135.5 million shares, roughly 43% of float in one widely followed dataset, underscoring how crowded positioning can contribute to sharp downswings like today’s. (marketbeat.com)