* GSK reports positive response in trial
* Will submit data for approval this year
* Result a fillip for GSK's comeback bid in oncology (Adds detail on class of drugs, rivals)
By Ludwig Burger and Pushkala Aripaka
Aug 23 (Reuters) - GlaxoSmithKline said an experimental multiple myeloma treatment has shown a meaningful response in patients that have run out of three previous treatment options, in a boost for the British drugmaker's cancer drug business.
Two doses of belantamab mafodotin helped subdue the disease in adults who had received three prior treatments for multiple myeloma, a cancer of the white blood cells, GSK said on Friday. The company intends to seek market approval and submit data from the trial to regulatory bodies this year.
GSK sold its approved oncology drugs to Novartis in 2014, but has staged a comeback in cancer treatment with a deal to buy U.S. firm Tesaro for $5.1 billion last year and an agreement in February to pay up to 3.7 billion euros ($4.09 billion) to Germany's Merck KGaA for the rights to a next-generation immunotherapy.
"We are on track to file belantamab mafodotin later this year and continue to investigate how it could help even more patients with this disease," GSK's Chief Scientific Officer Hal Barron said.
The drug targets a protein linked to multiple myeloma known as BCMA.
"This is yet another positive signal that GSK's R&D engine is being turned around and should be well received by the market," said Liberum analyst Graham Doyle.
In another recent win in oncology, GSK's Zejula - formerly Tesaro's lead compound - was shown to slow progression of ovarian cancer.
GSK shares were up 1% at 0923 GMT versus a 0.4% gain in the STOXX Europe 600 Health Care index.
Details of the belantamab mafodotin trial, which tracked how patients fared over time and did not feature a comparison group without the novel treatment, would be presented at an as yet undisclosed medical conference, the company added.
The interim result gives further credence to a class of molecules known as antibody drug conjugates (ADC) that belantamab mafodotin belongs to.
The concept further builds on the established method of using antibodies that block or bind to foreign substances in the body. ADC, in turn, are antibodies with a cell toxin as a molecular add-on.
That allows chemotherapeutic agents, which are harmful to all human cells, to be brought to cancer cells at much higher doses than in conventional chemotherapy.
AstraZeneca agreed in March agreed to pay up to $6.9 billion to work with Daiichi Sankyo on an ADC against breast cancer, in a challenge to another ADC called Kadcyla, made by Roche.
Multiple myeloma is the second most common form of blood cancer. While it can be treated, there is no available cure, GSK said.
The condition is expected to claim the lives of 13,000 people in the U.S. in 2019, according to the American Cancer Society.
The BCMA protein that is characteristic of multiple myeloma is also being used as a target in cell therapies developed by Johnson & Johnson, bluebird bio Inc, Celgene Corp.
($1 = 0.9036 euros) (Reporting by Pushkala Aripaka in Bengaluru; editing by Patrick Graham and Mike Harrison)