It should come as no surprise that Moderna stock booked a massive gain in the third quarter that easily made it the best-performer in the S&P 500. Some notable stocks, however, were major losers in the quarter.

Moderna stock has rallied since the company unveiled clinical updates to its cancer vaccine in collaboration with Merck in late August. Shares of Moderna rose 177% the day the cancer vaccine update was announced. For the quarter, the biopharmaceutical company surged 173%.

Citi's Geoff Meacham on Wednesday cut his rating on Moderna stock to Sell from Hold following what he called an "outsized run" in August.

CEO Stéphane Bancel said last week at Bernstein's annual healthcare conference that Moderna is an mRNA platform company, not just a maker of Covid-19 vaccines. The company is also expanding into oncology and rare diseases.

The other stocks rounding out the five best-performing S&P 500 stocks for the quarter were Everpure, Palantir Technologies, Veeva Systems, and Illumina.

As for the worst-performing stock in the quarter? That was Fair Isaac, maker of the FICO score.

Shares tumbled 49% over the past three months, but the bulk of that decline occurred Tuesday. FICO stock fell 26% and logged its worst daily percentage decline since 1989 after Bill Pulte, the director of the Federal Housing Finance Agency, said mortgage pricing will be simplified and that the new structure will incorporate VantageScore, a direct competitor to the FICO score.

Adding to the pain for FICO, Rocket Mortgage, part of Rocket Cos., said this week it will be the first mortgage lender to use VantageScore 4.0 as its preferred credit scoring model for all eligible loans.

These were just the latest signs that FICO could be losing its near credit score monopoly. FICO stock has been in a steep downtrend since November 2024, when it closed at a record high of $2,382.40.

Rounding out the five worst-performing S&P 500 stocks in the third quarter were AppLovin, Corning, Lennox International, and KLA.