A plan to give people in the United States easier access to unproven peptide drugs favored by Health Secretary Robert F. Kennedy Jr. was opposed by most Food and Drug Administration scientific staff members, who had limited input in drafting the policy, according to six people familiar with its development.

Calley Means, a top adviser to Health Secretary Robert F. Kennedy Jr. and a chief advocate for the Make America Healthy Again movement, resigned from his position with the Trump administration Thursday.