definiens: . Interim Period means the period beginning on the Amendment Effective Date and continuing untilthe earliest of ( a ) [COMPANY] ’s exercise of its Opt - in Right pursuant to Section 4A.2(a ), ( b ) the end of the Opt - in Periodafter [COMPANY] ’s receipt of a Study Completion Package, or ( c ) an ALN - RSV01 Failure . ” . Opt - in Fee means, subject to the terms of Section 4A.2(a ), the following : If [COMPANY] has met theSuccess Criteria specified under clause ( a ) of Part B of Exhibit K, but not the Success Criteria specified under clause(b ) of Part B of Exhibit K, the Opt - in Fee will mean [ * * ] percent ( [ * * ] % ) of the ALN - RSV01 Development Costs incurredby [COMPANY], payable in accordance with Section 4A.2(a ), for the Development of ALN - RSV01 in the Adult TransplantField during the Interim Period . If [COMPANY] has met the Success Criteria specified under clause ( b ) of Part B ofExhibit K, the Opt - in Fee will mean [ * * ] percent ( [ * * ] % ) of the ALN - RSV01 Development Costs incurred by [COMPANY], payable in accordance with Section 4A.2(a ), for the Development of ALN - RSV01 in the Adult Transplant Field duringthe Interim Period