A new drug that harnesses the immune system to attack tumours is highly effective against advanced bladder cancer, researchers, including one of Indian-origin, have found.
Injections of the experimental agent atezolizumab were found to shrink tumours by at least 30 per cent and stall new tumour growth in 28 of 119 (24 per cent) of patients.
All patients had received the medication as their initial therapy for the disease.
"Our new study results argue that atezolizumab represents a major advance in the treatment of bladder cancer," said Arjun Balar from New York University in the US.
"Atezolizumab is the first therapy to be approved in more three decades for this disease, and it is the new standard of care for patients whose initial therapy with platinum-based chemotherapy drugs has failed," said Balar.
"Indeed, it may be the only therapy some patients need," he added.
The current "first-line" standard of care in bladder cancer, is cisplatin, a drug that kills tumour cells by preventing them from repairing damage to their DNA.
In widespread use since the 1970s, cisplatin extends survival to slightly more than a year, but nearly half of bladder cancer patients, most of whom are elderly with other serious health issues, cannot take it because of its toxic side effects on nerve and kidney function, as well as hearing, researchers said.
Moreover, many patients' cancers develop drug resistance to cisplatin and similar chemotherapy medications over time, they said.
According to Balar, atezolizumab was well tolerated by all patients in the current study, which was conducted in medical centres across the US, Canada, and Europe.
Patients reported relatively mild instances of fatigue, itchy skin, and diarrhoea, which represented far fewer and less-severe side effects than seen with cisplatin or its common alternative, carboplatin, Balar said.
Half the patients who responded to the new therapy did so within 15 weeks, with almost all (21 out of 28) remaining on therapy without any detectable signs of cancer growth (at a dose of 1,200 milligrammes every three weeks).
Checkpoint inhibitors - some already approved to treat other forms of cancer - are designed to "retrain the immune system" to attack tumour cells by blocking the action of proteins believed to help cancer cells evade recognition by the immune system, said Balar.
Scientists say the new medication primarily blocks the interaction of the protein PD-L1, or programmed death ligand-1, with its programmed death receptor partner and checkpoint, PD-1.
This "lock and key" connection is critical to the detection of tumour cells by immune system T cells.
