(Bloomberg) -- Moderna Inc., whose initial public offering in December was one of the most hyped in biotech, gave investors their first look at its personalized cancer vaccine platform on Wednesday.

Twelve of the 13 patients who received Moderna’s mRNA-4157 as monotherapy after their solid tumors had been surgically removed are still disease-free after about eight months, according to an abstract released ahead of the American Society of Clinical Oncology annual meeting. In 20 patients with inoperable tumors, adding mRNA-4157 to Merck & Co.’s Keytruda led to two partial remissions and five patients had stable disease.

“These are early days,” Tal Zaks, Moderna’s chief medical officer, said in a phone interview. “Real proof of concept for vaccine combinations is going to come from much larger data sets.”

The treatment didn’t show any toxicities tied to dosing or any serious side effects. Moderna has already submitted plans to the Food and Drug Administration to pursue a mid-stage study in combination with Keytruda for skin cancer. Should the vaccine reach the market in years to come, Cambridge, Massachusetts-based Moderna would need to scale up manufacturing as it now takes roughly two months to manufacture one treatment.

Moderna’s vaccines aim to boost the body’s immune response and attack tumor cells by decoding protein fragments on a patient’s cancer cells and creating a unique corresponding cure.

The company’s shares fizzled after their debut but have rallied in 2019. While the stock is down 18% from its highs earlier this month, it’s still trading around the $23 a share IPO price. Wall Street analysts have remained bullish despite the volatility, saying sales of the vaccine platform could reach as high as $35 billion.

Additional study results will be presented at the ASCO meeting taking place May 31 through June 4 in Chicago.

To contact the reporter on this story: Cristin Flanagan in New York at cflanagan1@bloomberg.net

To contact the editors responsible for this story: Catherine Larkin at clarkin4@bloomberg.net, Scott Schnipper

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