US antitrust regulators are taking a good look at Roche's hostile takeover bid for Illumina, which has been repeatedly rejected by the gene specialist.

The Swiss major has received a request for additional information, known as a 'second request', from the US Federal Trade Commission. Specifically, the regulator is seeking more details about Roche’s existing microarray business.

The effect of the second request is to extend the waiting period on the proposed purchase until 10 days after Roche has "substantially complied" with the FTC's wishes. That period can be extended voluntarily by the company or terminated sooner by the FTC.

Roche said it will continue to work "closely and cooperatively "with the FTC as it conducts its review of the proposed transaction. However, any acquisition would appear to be some way off.

A fortnight ago, Roche extended its $5.70 billion hostile bid for Illumina, without raising its offer, to March 23. However, very few shares have been tendered by investors who have listened to Illumina's management, which in January adopted a 'poison pill' to ward off Roche's advances and  previously dismissed the offer as "grossly inadequate in multiple respects" and "opportunistic".