definiens: shall mean the compound known as L - FMAU, with the chemical name, 2 ’ -fluoro-5 - methyl - ß - L - arabinofuranosyluracil, including any salts and est ers thereof . BUKWANG acknowledges that viral resistance may limit the clinical utility and comme rcial potential of the Compounds . In the conduct of the BUKWANG Development Program, BUKWANG shall u se its best efforts to conduct, or shall cause its sublicensee to use its best efforts to co nduct, preclinical and clinical studies of the Compounds in combination with other anti - HBV drugs or drug candidates in order to determine whether in vitro, synergy, pharmacologic compatibil ity, differing resistance patterns, chemical structures, mechanisms of action or other factors o f the combination treatment regimens may limit or reduce the development of resistance to the Compoun ds . BUKWANG shall conduct, or shall cause its sublicensee to conduct, preclinical combination studies with at least two other drugs or drug candidates and shall use, or shall cause its sublic ensee to use, its best efforts to conduct clinical combination studies with as many other drugs or dru g candidates as it deems appropriate to determine the optimal combinations or sequence of c ombinations necessary to provide maximum efficacy against HBV and enhance the clinical utili ty and commercial potential of the Compounds