When Pfizer’s US Enbrel sales force gives way to Amgen’s in July, reps risk layoff if they don’t get picked up by Amgen or re-assigned to Pfizer’s new JAK inhibitor.

The news that Pfizer was turning over Enbrel sales duties in the US and Puerto Rico to Amgen, first reported by Dow Jones Newswires last week, caught reps off guard, a trusted source told MM&M. They had expected another year of detailing the 13-year-old biologic drug to specialist physicians, or perhaps to transition to Pfizer’s new JAK3 inhibitor tofacitinib, or possibly to sell both at same time, before expiration of the Pfizer/Amgen co-promotion term on October 31, 2013.

Now, none of those scenarios is a given. Neither company would say how many employees would be affected by the transition, which is effective July 23, or pinpoint the size of the current Enbrel field force. Specialty sales forces are typically much smaller than those for primary care, numbering in the hundreds rather than the thousands.

Pfizer said it will give Enbrel reps the option to apply to Amgen to keep selling the drug, or to stay on “and be considered for other internal opportunities.” One of those opportunities may include interviewing to sell tofacitinib, the drug Pfizer is developing which would compete with Enbrel.

Tofacitinib is an oral, small-molecule treatment for rheumatoid arthritis (RA) and psoriasis. An NDA was filed in December, and the FDA is scheduled to decide on the drug this August. Sanford Bernstein analyst Tim Anderson predicts sales of $1.7 billion by 2016.

If either of those options don’t work out, rumors abound that the reps could get pink slips. “Maybe not a layoff, but will be the end of the line for some,” said a post on CafePharma.com speculating about the fate of the Enbrel sales force. “Managers know who they will hire/retain,” said another poster on the thread, “BUT they have to go through the motions for legal reasons. Seen it too many times over the past 8 years.”

Pfizer and Amgen co-market Enbrel in the US and Canada and share profits from sales of the biologic there. The move, which firms said is designed to ensure better customer service, does not affect Pfizer’s Canadian sales staff, nor its US Enbrel marketing staff. Pfizer will also continue as exclusive seller of the drug outside North America, where it booked revenues of $3.7 billion last year (Amgen reported $3.5 billion in Enbrel sales from the US and Canada).

Amgen also announced that it is expanding the Enbrel sales force in the second half of 2012 but would not say how many new staffers it planned to bring on.

Amgen acquired the rights to Enbrel in July 2002 with its acquisition of Immunex, while Pfizer gained its rights to the biologic from its 2009 purchase of Wyeth. Amgen ran the dermatology business (the psoriasis indication), and Wyeth (then Pfizer) ran the rheumatology portion, which consists of four other indications. Enbrel was launched in the US in November 1998 and in Canada in March 2001 for the treatment of RA.

Tofacitinib is also being studied in several autoimmune conditions in addition to RA, including ankylosing spondylitis, psoriasis and psoriatic arthritis—indications that Enbrel competes in. Efficacy has reportedly been in line with current self-injectable products like Abbott’s Humira, with a possibly equal or somewhat better side effect profile.