The Federal Trade Commission posted letters on its web site sent to lawyers for Allos and Spectrum dated August 28 which said it had been investigating the deal but had closed the probe, indicating that the transaction could go forward.

Henderson, Nevada-based Spectrum agreed in April to buy Allos for about $1.82 per share or $206 million, after AMAG Pharmaceuticals Inc dropped its pursuit of the company last year.

Allos' lead drug Folotyn, which is used to treat relapsed or refractory peripheral T-cell lymphoma, had sales of about $50 million last year. Spectrum also makes Zevalin, a treatment for a different type of lymphoma. That had sales of $27 million.

Spectrum hopes to close the deal by September 4 or shortly thereafter, said Chief Executive Officer Rajesh Shrotriya.

(Reporting By Diane Bartz; editing by Carol Bishopric)

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