The scientist's groundbreaking research provided new insights into the disease's progression however, further studies are needed to confirm these findings.
Correct: C
The sentence presents two independent clauses: 'The scientist's groundbreaking research provided new insights into the disease's progression' and 'further studies are needed to confirm these findings.' When a conjunctive adverb like 'however' connects two independent clauses, it must be preceded by a semicolon and followed by a comma. Option C correctly applies this rule.