Amphastar Pharmaceuticals (NASDAQ: AMPH) disclosed that its subsidiary, International Medication Systems, Limited (IMS), received a warning letter from the U.S. Food and Drug Administration on July 2, 2026, related to its drug manufacturing facility in South El Monte, California.

The warning letter follows an FDA inspection of the facility conducted in December 2025, which resulted in inspectional observations recorded on an FDA Form 483. The FDA cited violations of current Good Manufacturing Practice (CGMP) regulations, specifically regarding investigation procedures, environmental monitoring and handling procedures, and manufacturing equipment.

The warning letter does not direct IMS to cease operations or restrict products from the facility, nor does it require a further recall, though the company noted this is subject to third-party verification. IMS said it continues to manufacture and supply products from the facility while implementing a remediation plan.

The FDA has requested that IMS submit an initial response within 15 working days, conduct a risk assessment, and submit a remediation plan. The company said it has been implementing corrective actions since the conclusion of the December 2025 inspection.

Amphastar stated it is evaluating the impact of the warning letter on its business operations and acknowledged it cannot provide assurance that the FDA will be satisfied with IMS's response or confirm the timing of resolution. The company noted that additional regulatory or legal action may be taken without further notice until the cited deficiencies are resolved.