Locally enhanced chemotherapy by electroporation: clinical experiences and perspective of use of electrochemotherapy

Electroporation is used to enhance drug diffusion and gene delivery into the cytosol. The combination of electroporation and cytotoxic drugs, electrochemotherapy (ECT), is used to treat metastatic tumor nodules located at the skin and subcutaneous tissue. The objective response rate following a single session of treatment exceeds 80%, with minimal toxicity for the patients. The efficacy of ECT in the bone and visceral metastasis is currently investigated, and Phase II studies have been completed. ECT has been used to treat skin primary tumors, except melanoma, and is under investigation for locally advanced pancreatic cancer. Early evidence suggests that treatment of tumor nodules with ECT recruits components of the immune system and eliciting a systemic immune response against cancer is a challenging clinical perspective. Considering the proven safety in several different clinical applications electroporation should be viewed as a clinical platform technology with wide perspectives for use in ECT, gene therapy and DNA vaccination.

Immune modulation in cancer with antibodies

Ipilimumab is the prototypical immunomodulatory antibody, approved by the FDA in 2011 for advanced melanoma on the basis of survival benefit. Since that time, we have made significant strides in optimizing this therapy: we have characterized the spectrum of immune-related adverse events and learned how to mitigate them with treatment algorithms, discovered potential biomarkers of activity, and identified the potential synergy between checkpoint modulation and other therapeutic modalities. Recent phase I trials have established the efficacy and safety of next-generation checkpoint agents, including PD-1 and PD-L1 inhibitors, across multiple tumor types. Much work lies ahead in developing these next-generation checkpoint agents, testing them in combination, and determining how to integrate them into the treatment paradigms of various tumor types.

Checkpoint blocking antibodies in cancer immunotherapy

Cancers can be recognized by the immune system, and the immune system may regulate and even eliminate tumors. The development of checkpoint blocking antibodies, such as those directed against cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programmed death 1 receptor (PD-1), have demonstrated significant recent promise in the treatment of an expanding list of malignancies. While both CTLA-4 and PD-1 function as negative regulators, each plays a non-redundant role in modulating immune responses. CTLA-4 attenuates the early activation of naïve and memory T cells. In contrast, PD-1 is primarily involved in modulating T cell activity in peripheral tissues via interaction with its ligands, PD-L1 and PD-L2. Unfortunately, not all patients respond to these therapies, and evaluation of biomarkers associated with clinical outcomes is ongoing. This review will examine the efficacy, toxicities, and clinical development of checkpoint blocking antibodies, including agents already approved by the US Food and Drug Administration (anti-CTLA-4, ipilimumab) or in development (anti-PD-1, PD-L1). Future studies will likely uncover new promising immunologic checkpoints to target alone or in combination with other immunotherapeutic approaches, chemotherapy, radiotherapy, and small molecules.