What is the ruling on a Muslim patient accepting to undergo an experimental trial of a new drug in exchange for money, knowing there is a possibility of side effects?

If it is possible to remove the potential harm from testing a new drug with permissible medications and alleviate its effect, whether done by the company or another party, then there is no objection to using it for testing, whether for compensation or as a donation. However, if the resulting harm could lead to irreparable damage, then it is not permissible to use it, even for a large sum of money, due to Allah’s saying: "And do not kill yourselves."