Complex sentence: The 40-year study was controversial for reasons related to ethical standards because researchers knowingly failed to treat patients appropriately after the 1940s validation of penicillin as an effective cure for the disease they were studying.
Split into simpler sentences: The 40-year study was controversial for reasons related to ethical standards. Researchers knowingly failed to treat patients appropriately after the 1940s validation of penicillin was found as an effective cure for the disease they were studying.