Inc. Chief Executive Officer Stephane Bancel said he believes the personalized mRNA cancer vaccine his company is developing with Merck & Co. will work in a variety of tumors, directly addressing a key issue shrouding the company’s future.

The novel vaccine’s potential has sent investors, doctors and patients on a rollercoaster ride in recent months. The companies disclosed in August that it reduced the recurrence of melanoma, the most deadly skin cancer, in a critical, late-stage study, without expounding. Details released in the past few days fell short of the high expectations some had for the novel approach, which uses the body’s own immune system to fight cancer.

The gyrations in Moderna’s shares show how important the technology is to the company, which is testing it in a variety of cancers. Called intismeran autogene, the vaccine is crafted for each patient using genetic information taken from their tumors. The bespoke approach allows the companies to shift the target, and it’s already being studied in kidney, lung and bladder cancers.

“We believe that it’s going to work in more cancers than melanoma,” Bancel said during an interview on Bloomberg Television. “I believe the kidney cancer should look positive.”The extent of the vaccine’s benefit has been a hot topic since the melanoma results started to emerge ahead of the formal presentation at the European Society for Medical Oncology meeting in Madrid on Oct. 24. While clearly positive, the findings nonetheless raised questions among some investors about how broadly applicable the approach is and whether it will work in other kinds of cancer.

“This doesn’t answer the question of if the encouraging melanoma signal will read across to the other indications.,” wrote Akash Tewari, an analyst at Jefferies, who estimates it may generate $4.6 billion in peak sales, in a note to clients on Oct. 22. “We’re TBD on this working in other settings.”The data suggests the benefit of the vaccine may increase over time, Tewari said in a subsequent note, after the results were presented.

A big trial kidney cancer trial could be one of the next ones to read out, potentially generating results by the end of this year or early next year, Bancel said at Bloomberg headquarters in New York after his television interview.

He expressed confidence that the personalized cancer shot will ultimately work on an array of tumor types. “I believe that it should work in all the tumors where Keytruda works,” he said during the interview, referring to Merck’s blockbuster cancer drug that is used to treat numerous cancers today.

While some investors are uncertain about the how easily the individualized production process for the vaccine can be scaled up, Bancel said creating the Covid-19 vaccine in the pandemic “was a much bigger challenge” than producing a personalized cancer shot.

When it comes to cancer, “We’ve already been working on it for years,” he said. “We have a lot of engineers. We’ve learned a lot from Covid that we can apply there,” he said.

The time to produce the vaccine, which took roughly nine weeks during the phase 3 trial, should fall over time as the company makes the process more efficient, he said.