The present invention relates to combination therapy with ADCs against a tumor-associated antigen, such as Trop-2, and drugs, such as microtubule inhibitors and/or PARP inhibitors. Where ADCs are used, they preferably incorporate SN-38 or another drug that induces DNA strand breaks. Preferably, the combination of ADC and PARPi or microtubule inhibitor exhibits synergistic effects against the cancer. The combination therapy can reduce solid tumors in size, reduce or eliminate metastases and is effective to treat cancers resistant to standard therapies, such as radiation therapy, chemotherapy or immunotherapy.