Drugmakers offered feedback on the FDA’s guidance for developing natural history studies for rare disease drug development, praising some parts of the guidance but calling for more details.

Lundbeck noted that many rare diseases have established disease registries made available by clinicians and institutions, calling on the agency to acknowledge that it may not always be feasible for sponsors to influence registry development. Establishing a free-standing prospective natural history study can be challenging in terms of recruitment as well, the drugmaker added.

The company also suggested electronic health records as a potential source for creating a control group. The agency should also consider how the guidance’s principles could apply to other vulnerable populations and pediatric development, Lundbeck said.

Merck asked the agency to clarify its expectations for data submissions. The company said it’s unclear if sponsors should submit only external control data or the whole natural history study.