The first Phase 3 data for a cancer vaccine has raised questions about whether the potential new treatment is needed.

Moderna's (MRNA) leaked cancer-vaccine trial results looked “promising” on the surface, yet the biotech stock came under intense pressure late on Thursday and was weak on Friday morning too, although the stock regained the losses and was trading higher later in the session. In fact, MRNA slipped through its 20-day moving average (MA) this week, indicating bears have taken back control of the near-term.

Moderna falls despite positive phase III cancer therapy data showing reduced melanoma recurrence and metastasis risks, as investors weigh elevated expectations.

Moderna (MRNA) shares plunged after a partial leak showed results for the company's cancer vaccine trial. As Alison Kosik points out, the results were positive but weren't enough for investors.

Beneath the chaos surrounding Moderna and Merck's latest data on their personalized cancer vaccine, oncologists see something else: an important milestone in melanoma treatment. The companies on Thursday released detailed results from a Phase 3 trial on their mRNA-based shot after partial data leaked on social media platforms earlier that day.

Moderna and Merck's cancer vaccine reduced the risk of melanoma recurrence or death by 42%, but investors questioned its potential across other cancers.

Moderna has soared this year amid optimism about its personalized cancer vaccine candidate. Investors are closely following data from that candidate's phase 3 trial.

Full late-stage results for the personalized melanoma vaccine from Moderna (NASDAQ:MRNA | MRNA Price Prediction) and Merck (NYSE:MRK) came back positive, yet the selling hasn't stopped. Those numbers landed short of the loftiest hopes built into a long rally.