Ribavirin is also a polymerase inhibitor, right? So, any developer of similar drugs has to compare them against Rib wrt efficacy and side effect. If the comparison is not favorable against Rib, the drug should not be developed.
Rib is a synthetic nucleoside. It is a nucleoside analog which will be incorporated into viral code by RNA or DNA synthesis by error, and the result is inhibition of the synthesis. It should be like polymerase inhibitor drugs against HBV. Gilead is expert in the area. GILD is so successful in developing new drugs against HBV, but all they are doing is combining two different nucleoside analogs, one is a polymerase inhibitor and the other is a reverse transcriptase inhibitor, and combining again the two with a third by another company.