these advances are turning what was once an eventual death sentence into manageable condition.

위 문장에서 what 부분에 주어가 생략된게 these advances가생략된건가요?

그렇다면 what은 명사절 즁주어절인거 같은데 그럼 저 문장은

1. these advances are turning.

2. these advances was once an eventual death sentence into manageable condition

이게 맞나요?? ㅠㅠ