MIAMI, Nov 1: Two new “smart bomb” drugs that target specific proteins needed for tumour growth have produced promising results in clinical trials against a number of cancers, scientists said on Thursday.

Data on the treatments, developed by Anglo-Swedish group AstraZeneca Plc and ImClone Systems Inc, was presented at an American Association for Cancer Research conference.

AstraZeneca’s tablet Iressa and ImClone’s competing injectable product C225 are the first in a new class of drugs that block the epidermal growth factor receptor (EGFR), a biochemical “switch” which promotes tumour cell growth.

Both drugs aim to knock out cancer cells without damaging healthy tissue, and are the fruit of recent advances in molecular biology that have allowed scientists to unpick the way cancer cells live and die.

Dr Jose Baselga of Vall d’Hebron University Hospital in Barcelona, Spain, said Iressa was a significant step forward in the treatment of non-small-cell lung cancer, a major killer.

“It is almost unprecedented to see such a high response rate with a new drug in such a difficult-to-treat subset of patients,” he said.

Phase II trial results showed Iressa succeeded in shrinking lung tumours by at least half in 18.7 percent of seriously ill patients who failed to respond to conventional chemotherapy. In 52.9 percent of patients the disease stabilised, while in 34 percent the cancer had not grown after four months.

A summary of the trial results, which involved 209 patients, had been released on the Internet earlier this month.

Baselga said the overall response rate was “much higher” than with standard chemotherapy, while the side effects — primarily diarrhoea and skin rash — were minimal.

Additional early Phase I data presented at the meeting also showed the potential of Iressa in a wider range of solid tumour types and highlighted its potential use in combination with existing anti-cancer drugs.

Meanwhile, results of a Phase II trial on ImClone’s drug showed 24 percent of head and neck cancer patients who had not responded to standard treatment were helped by a combination of C225 plus cisplatin, an established anti-cancer drug.

“This is encouraging compared with other second-line therapies, which induce response in less than five percent of patients,” said Roy Herbst, of the University of Texas MD Anderson Cancer Center in Houston.

Both Iressa and C225 — which ImClone will market with Bristol-Myers Squibb Co and Germany’s Merck KGaA — are slated to reach the market next year and are already being toted by financial analysts as potential $1-billion-a-year products.

ImClone’s antibody drug is expected to be approved for the treatment of colon cancer early next year, some six months or so ahead of Iressa.—Reuters