Washington (CNN) President Donald Trump signed the "Right to Try Act" Wednesday, a measure aimed at helping terminally ill patients access drug treatments that are yet to be fully approved by the Food and Drug Administration.

Trump, at a White House ceremony surrounded by patients and families who will be affected by the legislation, said his administration "worked hard on this" but said repeatedly he didn't understand why it hadn't been done before.

The bill will give terminally ill patients the right to seek drug treatments that remain in clinical trials and "have passed Phase 1 of the Food and Drug Administration's approval process" but have not been fully approved by the FDA. Some opponents of the bill argue that the legislation won't change much but could have a detrimental effect on how the FDA safeguards public health.

Trump said he thinks "hundreds of thousands" could be saved as a result of the legislation.

"With the passage of this bill, Americans will be able to seek cures," Trump said adding they will finally be given "the right to try."

Read More