Former President Jimmy Carter said this week that he has received the second of four planned doses of a drug to fight the cancer that has spread to his brain.

Nearly a month after revealing the cancer, the 90-year-old former president has stepped back from work at the human rights organization he founded after leaving the White House, Fox News reports.

But he and his wife, Rosalynn, updated a capacity crowd of 450 on The Carter Center’s work Tuesday evening.

Carter said no further radiation treatments are planned for the four tumors he has.

He added that he has experienced no “ill effects” after recently receiving a second dose of Keytruda, a recently approved drug to help the immune system seek out and destroy cancer cells.

“And we’ll know what the positive effects are later on,” he said.

Carter said he’s grateful that his doctors scaled back the amount of water he must drink every day, while receiving treatment.

“The doctors have been nice enough to cut me back to 64 ounces a day. Instead of getting productive work done, I spent a lot of time in the restroom,” he said.