definiens: shall mean the periodbetween the date of this Letter Agreement and the date when the earliest of the followingshall occur : ( i ) the aggregate number of Dupilumab / REGN3500 Eligible InvestmentShares sold pursuant to this Letter Agreement ( including both Dupilumab / REGN3500Eligible Investment Shares to be Purchased and Open - Market Dupilumab / REGN3500Eligible Investment Shares ) equals the Dupilumab / REGN3500 Eligible Investment ShareSale Cap ; ( ii ) if a Purchaser Party does not submit a Dupilumab / REGN3500 EligibleInvestment Sale Notice in respect of the Dupilumab / REGN3500 Eligible InvestmentStatement for the last Dupilumab / REGN3500 Eligible Investment Covered Period, thelast day of any then - existing Dupilumab / REGN3500 Eligible Investment Sale Period ; ( iii)the end of the Dupilumab / REGN3500 Eligible Investment Sale Period relating to the lastDupilumab / REGN3500 Eligible Investment Covered Period in respect of which aPurchaser Party submits a Dupilumab / REGN3500 Eligible Investment Sale Notice ; and(iv ) the effective date of termination of the Antibody LCA pursuant to its terms ( includingSection 19.7 of the Antibody LCA )