By Bill Berkrot
May 15 (Reuters) - An experimental Roche Holding AG drug that helps the immune system attack tumors was well tolerated and demonstrated an impressive effect against a variety of cancers, according to preliminary trial results released on Wednesday.
While clinical testing of the drug is still in its early phases, the Roche treatment is considered one of the most promising in a new class of immunotherapies being developed by global drugmakers.
The drug, called MPDL3280A, significantly shrank tumors in 21 percent of 140 patients with advanced melanoma, lung cancer or kidney cancer, according to data from a scientific abstract of the Phase I study. Of the 29 patients whose cancer responded to the drug, 26 continued to respond - some more than a year after starting treatment - researchers said.
The study will be presented at the American Society of Clinical Oncology meeting in Chicago in early June.
Deutsche Bank analyst Tim Race, in a research note, said with this drug Roche "potentially has a greater than $5 billion product with potential for durable benefit across multiple cancers."
Roche's drug is an engineered antibody that targets a protein called PD-L1 on cancerous tumors, a defense mechanism that tumors use to trick the immune system's T cells into remaining inactive. Once the T cells can recognize the cancer, they grow and multiply to more efficiently attack it.
"We have seen really amazing responses in lung cancer, in kidney cancer, in melanoma," Dr Roy Herbst, the study's lead investigator, said in an interview.
Broken down by cancer type, the response rate so far has been 31 percent in melanoma, 22 percent in lung cancer and 13 percent in kidney cancer, the available data showed.
The study has since been expanded to include patients with colon, bladder and head and neck cancers, researchers said.
NO SERIOUS SIDE EFFECTS SEEN
MPDL3280A, which was administered intravenously every three weeks, attacks a different target than a similar class of highly promising immunotherapies called PD-1 inhibitors being developed by Bristol-Myers Squibb, Merck & Co and others.
Roche and some researchers believe the anti-PDL1 medicine is more selective than the PD-1 drugs and may lead to less inflammation of the lung and other organs.
The Roche drug was well tolerated in the study, Herbst said: There were no side effects that required limiting the dosing.
"Most of the adverse events were transient and of low significance. We haven't seen any patients with significant inflammation of lung," said Herbst, chief of medical oncology at Yale Cancer Center in New Haven, Connecticut.
The data on progression-free survival, or the average time before a cancer begins to worsen, was not yet complete, and it will be a while before an overall survival benefit can be determined. But Herbst found the results thus far compelling.
"The progression-free survival for refractory lung, melanoma and renal cancers is impressive compared to historical controls," he said. "This is an incredibly interesting approach for cancer. It's showing efficacy. We're still learning how to select the patients properly."
Toward that end Roche is developing a diagnostic tool to identify those most likely to benefit from the treatment, such as those who test positive for the PDL1 protein.
Based on the trial's results, Roche said it will begin a larger study of its anti-PDL1 drug in patients with non-small-cell lung cancer that could be used to seek approval of the medicine.