Genentech has stopped a clinical trial of a peanut-allergy treatment over safety concerns about some reactions and not the drug itself.

Genentech said two children in the 150-person study had 'severe hypersensitivity reactions' when given a trace amount of peanut protein. They were given the protein to gauge the severity of their allergy. Neither child had received the drug, Xolair, the company said.

A phase II trial involving Xolair was stopped because of hypersensitivity reactions, according to Genentech chief executive officer, Art Levinson.

Along with co-developers Novartis AG and Tanox Inc., Genentech is testing Xolair as a treatment for peanut allergy. The injectable drug prevents the immune system from over reacting and obstructing airways, claim media reports.

Genentech may consider moving to a large-scale trial that would not include a peanut allergic-reaction test. Instead, such a trial would track patients over a long period of time to see if those receiving Xolair have fewer accidental peanut reactions than those taking a placebo.

"Genentech will discuss alternative plans for the peanut-allergy treatment with the US Food and Drug Administration early this year," said Levinson.

Peanut allergy affects an estimated 1.5 million Americans. It can lead to potentially fatal anaphylactic shock if allergic individuals ingest even a trace amount of peanut flour or oil.

Genentech is a leading biotechnology company that discovers, develops, manufactures and commercialises bio-therapeutics for significant unmet medical needs.