CNBC's Jim Cramer said Friday he did not think investors were properly factoring in the likelihood a successful antiviral treatment for COVID-19 is developed.

"Is anyone even thinking anymore that there is something going on at any drug company that actually may have an antiviral?" Cramer said on "Squawk on the Street." "I have just been marveling that people think our drug companies don't have good scientists. … You're betting against science if you're betting long-term short here."

Cramer said the market is poised to take off for real if an effective treatment for COVID-19 is discovered.

"What happens if we actually find an antiviral that gets people out of the hospital? Could you imagine where this market is with this liquidity?" Cramer said.

Cramer's comments came as the Dow Jones Industrial Average tumbled more than 800 points on Friday, continuing the stock market's stretch of extreme volatility in response to the coronavirus pandemic.

The Dow on Thursday soared more than 1,350 points, or 6.4%, giving the 30-stock index its biggest three-session winning streak since 1931. The gains came as investors responded to Washington's progress on a $2 trillion economic stimulus bill.

The S&P 500, which gained 6.4% on Thursday, is down more than 3% on Friday.

The Dow and S&P 500 remain in bear market territory, sitting more than 20% below their February highs, despite their mid-week gains.

Cramer noted that clinical trials are underway in the U.S., where confirmed cases of COVID-19 have surpassed 86,000.

A large-scale clinical trial to determine how effective an existing anti-malaria drug is at treating COVID-19 began Tuesday in New York state.

Additionally, pharmaceutical companies such as Regeneron are developing therapeutics while Moderna Therapeutics and Sanofi Pasteur are working on vaccines.

Health officials have repeatedly stressed that developing new drugs and vaccines is a difficult process that can take months and even years.

But there is some optimism among health officials such as Northwell Health CEO Michael Dowling, who told CNBC on Thursday that trials underway at his hospital system are showing signs of progress.

Northwell Health, the largest health-care provider in New York state, is working with Regeneron and Gilead Sciences to test the efficacy of existing drugs. The trials have not produced "definitive results yet," Dowling cautioned on "Squawk on the Street."

"But I am pretty certain that within the next week or two, we're going to find out that one or more of these drugs do make a difference and that would obviously change the landscape when that happens," Dowling said.