AstraZeneca and partner Palatin Technologies have halted a Phase I trial of an investigational obesity drug after a participant fell ill.

The safety review committee established by AstraZeneca, which was conducting the trial, has stopped the study of AZD2820 after a serious adverse event was reported. The drug is a subcutaneously-administered peptide melanocortin-4 receptor partial agonist.

It is suspected the subject may have had an allergic reaction following his first dose and Palatin chief executive Carl Spana said "we are pleased the subject has fully recovered from this unfortunate adverse event". He added that "we will work closely with AstraZeneca to investigate the cause of this incident and the overall plans for the AZD2820 programme".

The study targeted enrolling 72 obese but otherwise healthy male subjects, and 11 had completed their dosing regimen prior to the halting of the trial. Palatin noted that another Phase I single-ascending dose study of AZD2820 was finalised in 2011 without any reported serious adverse events.

Mr Spana added that AstraZeneca "has confirmed their remaining commitment to the continued advancement of melanocortin agonists for treatment of obesity", including a number of collaboration compounds in various stages of preclinical testing. The firms signed the obesity pact in 2007.

Meantime, the Anglo-Swedish drugmaker has announced that it has completed the acquisition of the USA's Ardea Biosciences.

AstraZeneca is paying $32 per share, which represents a premium of 54% on Ardea's closing price on April 20. Excluding the latter's cash, the purchase values the San Diego-based company at $1 billion.

For its money, AstraZeneca is getting hold of lesinurad (formerly known as RDEA594), which is currently in Phase III for the chronic management of hyperuricaemia in patients with gout.