21 C.F.R. § 814.40
Within 180 days after receipt of an application that is accepted for filing and to which the applicant does not submit a major amendment, FDA will review the PMA and, after receiving the report and recommendation of the appropriate FDA advisory committee, send the applicant an approval order under § 814.44(d) , an approvable letter under § 814.44(e) , a not approvable letter under § 814.44(f) , or an order denying approval under § 814.45 . The approvable letter and the not approvable letter will provide an opportunity for the applicant to amend or withdraw the application, or to consider the letter to be a denial of approval of the PMA under § 814.45 and to request administrative review under section 515 (d)(4) and (g) of the act.
21 C.F.R. §814.40