By Ransdell Pierson

April 20 (Reuters) - A new type of immuno-oncology treatment from Novartis AG proved safe in a tiny study of three types of solid tumors, but the trial included too few patients and used too small a dose of the experimental product to prove effectiveness, according to data presented at a cancer meeting on Sunday.

The so-called CAR T cell is among a wave of new cancer treatments created by removing T cells, powerful immune system cells, from a patient's body and attaching an antibody fragment that enables them to recognize and target specific proteins on cancer cells. The souped-up T cells are then reinfused into the patient.

In clinical trials by Novartis and other drugmakers, CAR T cells have proven highly effective and relatively safe against blood cancers, such as leukemias and lymphomas. But the cells' safety and efficacy against solid tumors was largely untested.

The new Novartis-sponsored study, conducted by scientists at the University of Pennsylvania and presented at the annual meeting of the American Association for Cancer Research, enrolled six patients who had failed to benefit from standard treatments for ovarian cancer, pancreatic cancer or mesothelioma (a cancer in the protective lining covering many of the body's internal organs).

The treatment is designed to attack tumors carrying a protein on their surfaces called mesothelin, which is found in great numbers on cancer cells, particularly those of the ovaries and mesothelium.

One of the biggest concerns was whether the CAR T cells would attack healthy tissues, but that was not seen.

Penn oncologist Janos Tanyi, who helped lead the Phase 1 study, said the trial met its primary goal of safety, with no major adverse events seen after 28 days of treatment. But neither did any of the patients' tumors shrink.

The experimental therapy will soon be tested in larger numbers of patients, and in higher doses that have a better chance of proving effective, Tanyi said in an interview.

"At the beginning we had to go slow because of safety concerns," he said. "I expect much more effectiveness" in the next stages of the study.

Shares of numerous other companies developing CAR T cells, including Kite Pharma, Bluebird bio, Juno Therapeutics Inc and Ziopharm Oncology Inc, fell sharply on Monday on investor concerns about the absence of effectiveness in the Novartis study, according to industry analysts. Shares of the far larger Novartis rose 0.5 percent, however, amid an upturn in the broad stock market.

"Much more work remains before we can have confidence that CAR T therapy will be able to access the solid tumor market," Morgan Stanley analyst Matthew Harrison said in a research note.

(Reporting by Ransdell Pierson; Editing by Ted Botha)