H-1B transfer from previous employer when petition was never used

Hi,I had got an Approved H-1B from Employer A in FY 16 and the petition is valid till 12/31/2017. I have the I-797B, Notice of Action with me. But I never used the petition and left employer A.Now I am working for Employer B and I want to file for transfer of H-1B. My query is:

Is this transfer (filing of cap exempt petition) possible since the visa is not activated (I never traveled)? Do I need to give any documents other that the I-797B to my current employer B to file for transfer ?Regards

Please go thru this…