The founder and executive director of Drug Policy Alliance, Ethan Nadelmann, has announced he is vacating his post in a letter posted online.

“This is just about the toughest decision I’ve ever made but it feels like the right time for me personally and also for DPA,” he wrote.

The DPA followed with its own statement on Twitter: “We are so grateful for everything you did to help shape the movement to end the war on drugs, Ethan, and we are indebted to your leadership.”

Nadelmann identified a likely successor as head of DPA: Former deputy executive director Derek Hodel will become the interim executive director until a permanent replacement is chosen.

Nadelmann said his decision wasn’t driven by hopelessness over having to deal with the Trump administration.

“I had strongly hoped and assumed, as I came to this decision, that Donald Trump would not be our next president. That development did indeed give me pause but not change my mind. His administration will surely hamper our progress at the federal level but do little to undermine our progress and prospects in the states and cities where so much of our work has focused”