FCC recently issued regulatory rules for the reuse of the underutilized TV white space spectrum without negative impact on digital television broadcasts. Cognitive Radio techniques are of great importance to acquire opportunistic access to the TV bands. Since primary user may experience out-of-band power leakage from the secondary signal, Cosine-Modulated Filter Banks are considered as interesting alternatives to traditional OFDMs for spectrum pooling, due to their small sideband power leakage and spectral efficiency. In this paper, we propose a Nearly Perfect Reconstruction CMFB system for CR. A new objective function is provided to control the tradeoff between the level of interference caused by secondary transmission to primary users and the spectral efficiency of secondary users. An adaptive linear search optimization technique is employed for the prototype filter design. Simulation results show a significant enhancement in terms of BER, sideband power rejection, sidelobe radiation and effective throughput compared to conventional OFDM.