Hormone replacement therapies have long been approved by the Food and Drug Administration for use by cisgender patients, such as women who take estrogen when going through menopause. Now, for the first time, a nonprofit group is pursuing research with the goal of FDA approval for the use of estrogen as a gender-affirming treatment for trans and gender-diverse patients.

The group, the Research Institute for Gender Therapeutics (RIGT), was founded earlier this year with the mission of obtaining approval for gender-affirming hormones, which are currently prescribed to patients off-label without an explicit approval for trans health care. RIGT submitted a development plan to the FDA for a phase III clinical trial focused on estradiol — the most common form of estrogen for hormone treatments — and received the agency’s written feedback on Nov. 17 in lieu of a live pre-investigational new drug meeting.

In response to the group’s plan, the FDA “positively surprised” the group by advising them not to do a placebo-controlled trial, said Brad Sippy, RIGT’s founding director and president. The FDA also suggested widening the study’s population to include adolescents as young as 13 years old. The feedback comes at a time when many states are banning hormone treatment and puberty blockers for youth.

“[The FDA’s] feedback validates that this [gender incongruence] is a treatable condition and validates the existence of that population, and really gives us a pretty clear path to a federal approval for gender-affirming care,” said Sippy.