Image copyright Getty Images Image caption Nine-year-old Jordan McLinn, who has muscular dystrophy, shook Mr Trump's hand

President Donald Trump has signed a bill giving terminally ill patients the right to try experimental treatments not approved by the government.

Patients were able to apply to the US Food and Drug Administration (FDA) for access to non-approved drugs before, and most were granted permission.

The new bill does not mandate that drug makers give access to unapproved drugs to patients asking for them.

Advocacy groups including the American Cancer Society had opposed the bill.

"America is a nation of fighters. We never give up, right?" Mr Trump said to patients and their families during a bill signing ceremony at the White House on Wednesday.

After signing the bill, Mr Trump handed his pen to nine-year-old Jordan McLinn, who has been diagnosed with a form of terminal muscular dystrophy.

Jordan, who the bill is named for, has been accepted into a clinical programme in Chicago where he has been receiving weekly infusions.

He and his mother, Laura, had travelled from Indianapolis for the White House event.

Image copyright Getty Images

What has changed with the Right to Try act?

The new Right to Try act allows patients with life-threatening diseases to bypass the FDA's application process for " compassionate use " of experimental drugs.

Patients seeking access to "investigational drugs" now need only the approval of their physician and the drug manufacturer.

The new bill protects doctors and companies from the legal risks of allowing unapproved treatments unless they intentionally harm a patient.

The policy that patients must have exhausted all other approved treatments and clinical trial options remains.

In Mr Trump's State of the Union address in January, he called upon Congress to pass the bill, saying "patients with terminal conditions, and terminal illness, should have access to experimental treatment immediately" and "should not have to go from country to country to seek a cure".

What have the concerns been?

FDA commissioner Scott Gottlieb, a physician and a cancer survivor, had expressed concerns to Congress last year even as he said the agency was ready to implement the bill.

"The clinical trial process is crucial to the development of innovative new medical products that can improve or save patients' lives," he said to Congress.

Dr Gottlieb said there had to be a balance between giving patients access to investigational therapies and testing that ensures new products are safe and effective.

Under the FDA's prior rules governing "compassionate use", 99% of patient applications have been granted since 2009. Most requests are granted within a few days, and in emergency situations, often immediately via phone.

Image copyright Getty Images Image caption Commissioner Scott Gottlieb expressed concerns about the bill to Congress last year

Notably, going through the FDA allows the agency to modify experimental treatments to individuals to improve patient safety.

Advocacy groups who opposed the bill claimed it gives patients false hope since pharmaceutical companies are not required to give terminally ill patients the experimental treatments they might request.

In a letter addressed to Speaker Paul Ryan and Democratic leader Nancy Pelosi, 38 groups said removing the FDA from the equation would "likely do more harm than good".

Forty states have passed Right to Try laws of their own.

How are drugs approved by the FDA?

In order to be approved by the FDA, drugs must go through several phases of clinical trials . The process often means years of testing.

First, the drug manufacturer must prove the drug is safe for humans. These trials can have as few as 30 patients, and 70% of drugs move to the next trial.

Then, the manufacturer must prove the drug is an effective treatment for the condition it is being marketed for. Importantly, the drug cannot have severe side effects.

Only 33% of drugs proposed make it through this stage.

During the next phase, which can take up to four years, the company must test the drug on 300 to 3,000 patients with the disease the drug is designed to treat.