It's around 10-15% for the whole drug I-III flow (13.8% according to [1]), but that varies dramatically based on therapeutic area. On the order of a third of infectious disease vaccines might be approved but only maybe 5% of oncology therapies because the latter often have a different standard for approval so it's cheaper to run trials.
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6409418/