** Shares of Enanta Pharmaceuticals ENTA.O down 8% at $11.01 post-market after biotech firm launches follow-on
** Watertown, Massachusetts-based ENTA commences $50 mln stock offering
** JP Morgan, Jefferies and Evercore are joint bookrunners
** On Mon, ENTA shares surged 92% to close at $15.16 after co said its RSV treatment significantly quickened recovery in mid-stage study
** On Tues, stock ended down 21% at $11.97
** ENTA intends to use net offering proceeds to fund clinical trials, R&D, among other purposes, per the prospectus
** It has ~21.4 mln shares outstanding for roughly $256 mln market cap through Tues
** 5 of 7 analysts rate the stock "strong buy" or "buy" and 2 rate "hold"; median PT is $20, according to LSEG data
(Lance Tupper is a Reuters market analyst. The views expressed are his own)
((lance.tupper@tr.com 1-646-279-6380))