Antibody-drug conjugate (ADC) which delivers cytotoxic drugs specifically into targeted cells through internalization and lysosomal trafficking has emerged as an effective cancer therapy. We show that a bivalent biparatopic antibody targeting two non-overlapping epitopes on HER2 can induce HER2 receptor clustering, which in turn promotes robust internalization, lysosomal trafficking, and degradation. When conjugated with a tubulysin-based microtubule inhibitor, the biparatopic ADC demonstrates superior anti-tumor activity over ado-trastuzumab emtansine (T-DM1) in tumor models representing various patient subpopulations, including T-DM1 eligible, T-DM1 ineligible, and T-DM1 relapsed/refractory. Our findings indicate that this biparatopic ADC has promising potential as an effective therapy for metastatic breast cancer and a broader patient population may benefit from this unique HER2-targeting ADC.

Based on the previously described roles of doxorubicin in immunogenic cell death, both doxorubicin and liposomal doxorubicin (Doxil) were evaluated for their ability to boost the antitumor response of different cancer immunotherapies including checkpoint blockers (anti–PD-L1, PD-1, and CTLA-4 mAbs) and TNF receptor agonists (OX40 and GITR ligand fusion proteins) in syngeneic mouse models. In a preventative CT26 mouse tumor model, both doxorubicin and Doxil synergized with anti–PD-1 and CTLA-4 mAbs. Doxil was active when CT26 tumors were grown in immunocompetent mice but not immunocompromised mice, demonstrating that Doxil activity is increased in the presence of a functional immune system. Using established tumors and maximally efficacious doses of Doxil and cancer immunotherapies in either CT26 or MCA205 tumor models, combination groups produced strong synergistic antitumor effects, a larger percentage of complete responders, and increased survival. In vivo pharmacodynamic studies showed that Doxil treatment decreased the percentage of tumor-infiltrating regulatory T cells and, in combination with anti–PD-L1, increased the percentage of tumor-infiltrating CD8+ T cells. In the tumor, Doxil administration increased CD80 expression on mature dendritic cells. CD80 expression was also increased on both monocytic and granulocytic myeloid cells, suggesting that Doxil may induce these tumor-infiltrating cells to elicit a costimulatory phenotype capable of activating an antitumor T-cell response. These results uncover a novel role for Doxil in immunomodulation and support the use of Doxil in combination with checkpoint blockade or TNFR agonists to increase response rates and antitumor activity.

No abstract

In the originally published version of this article, in Figure 2E the representative immunoblots of lysates from antibody-treated cells did not indicate spliced lines between lane 7 and lane 8. When preparing the figure for publication, these lanes had been spliced together from the same immunoblot, as indicated in the corrected Figure 2E shown here, to remove an irrelevant lane. The authors apologize for any confusion this may have caused.948 Cancer Cell 35, 948-949, June 10, 2019 ª 2019 Elsevier Inc.

Immunogenic cell death (ICD) is the process by which certain cytotoxic drugs induce apoptosis of tumor cells in a manner that stimulates the immune system. In this study, we investigated whether antibody-drug conjugates (ADCS) conjugated with pyrrolobenzodiazepine dimer (PBD) or tubulysin payloads induce ICD, modulate the immune microenvironment, and could combine with immuno-oncology drugs to enhance antitumor activity. We show that these payloads on their own induced an immune response that prevented the growth of tumors following subsequent tumor cell challenge. ADCs had greater antitumor activity in immunocompetent versus immunodeficient mice, demonstrating a contribution of the immune system to the antitumor activity of these ADCs. ADCs also induced immunologic memory. In the CT26 model, depletion of CD8 T cells abrogated the activity of ADCs when used alone or in combination with a PD-L1 antibody, confirming a role for T cells in antitumor activity. Combinations of ADCs with immuno-oncology drugs, including PD-1 or PD-L1 antibodies, OX40 ligand, or GITR ligand fusion proteins, produced synergistic antitumor responses. Importantly, synergy was observed in some cases with suboptimal doses of ADCs, potentially providing an approach to achieve potent antitumor responses while minimizing ADC-induced toxicity. Immunophenotyping studies in different tumor models revealed broad immunomodulation of lymphoid and myeloid cells by ADC and ADC/immuno-oncology combinations. These results suggest that it may be possible to develop novel combinatorial therapies with PBD- and tubulysin-based ADC and immuno-oncology drugs that may increase clinical responses. .