Read MoreThis is biotech's real problem
The oncology company, which has one FDA-approved therapy to treat a form of brain cancer under its belt, opened for trading at $20.16, after pricing 12.5 million shares at $22.
This was below the $23 to $24 revised IPO range.
In a CNBC "Power Lunch" exclusive on Friday, Novocure executive chairman William Doyle said "Markets will be choppy they will go up and down, but I think if we take care of the cancer patients, stockholders are going to be in good shape in the long term and we're going to focus on the core mission."
Doyle, who is also a member of the investment management committee at Bill Ackman's hedge fund, Pershing Square Capital Management, addressed drug pricing pressures facing the biotech sector.
"These therapies can be expensive," said Doyle. "But even though we're not yet profitable there's never been a patient that's been denied the Novocure therapy."
Underwriters of Novocure's IPO include Deutsche Bank, JPMorgan Chase, Wells Fargo, JMP Securities, Evercore ISI and Wedbush PacGrow.