Dear Mohammad Nurunnabi , IRB does not provide guarantees.

Flying Blind: How Thorough are IRBs when Assessing Scientific Value?

"Institutional Review Boards (IRBs) in the United States play a crucial role in ensuring the ethical conduct of clinical trials, including assessing the scientific merit of studies to justify the risks to participants. However, prior research suggests that many IRBs do not systematically evaluate scientific merit, raising concerns about the approval of low-quality trials.

Objective is to investigate whether IRBs provide adequate guidance on assessing scientific merit in their Standard Operating Procedures (SOPs) and other relevant materials...

IRB guidance materials vary in their coverage of scientific merit dimensions, with significant gaps in areas critical for assessing study quality. Strengthening guidance materials by including comprehensive instructions for all 15 dimensions could improve IRB assessments of scientific merit, thereby enhancing the ethical oversight of clinical trials..."

https://link.springer.com/article/10.1007/s11606-024-09286-5

Sometimes, people conduct research without the approval of an ethics committee, sometimes due to a lack of knowledge, and other times because they are working on topics that were prohibited in the country at the time. One solution is to request an ex post approval, meaning presenting the research for review by a committee after it has been conducted. In a study on medical cannabis, where its use was not permitted in Argentina at the time the research was conducted, we requested—and obtained—ex post approval.