Tremelimumab: a review of development to date in solid tumors

Primary 4T1 tumor resection provides critical "window of opportunity" for immunotherapy

It is believed that primary tumor resection modulates host-tumor immune interaction, but this has not been characterized in a stringent breast cancer tumor model. This report, using the 4T1 murine mammary tumor model, characterizes for the first time the dynamic longitudinal changes in immunosuppressive and effector components of the immune system after resection of an established orthotopic primary tumor with a defined natural history of developing lung metastases. More specifically, we analyzed changes of absolute numbers and frequencies of MDSC, regulatory T cells (Treg), as well as activated CD4 and CD8 positive T cells in spleens and, in some studies, lungs of 4T1 tumor-bearing mice and mice after primary tumor resection. Importantly, using mathematical analyses we established that primary resection of an orthotopic tumor had created a "window of opportunity" with decreased tumor-associated immune suppression that existed for approximately 10 days. Although tumor resection did slightly prolong survival, it did not affect the ultimate development of metastatic disease since animals with resected tumors or intact primary tumors eventually died by day 47 and 43, respectively. This window of opportunity likely occurs in humans providing a rationale and parameters for integration and testing of immunotherapeutic strategies in this critical "window of opportunity" to combat the development of metastatic disease.

Trial Watch: Immunostimulatory monoclonal antibodies in cancer therapy

Immunostimulatory monoclonal antibodies (mAbs) exert antineoplastic effects by eliciting a novel or reinstating a pre-existing antitumor immune response. Most often, immunostimulatory mAbs activate T lymphocytes or natural killer (NK) cells by inhibiting immunosuppressive receptors, such as cytotoxic T lymphocyte-associated protein 4 (CTLA4) or programmed cell death 1 (PDCD1, best known as PD-1), or by engaging co-stimulatory receptors, like CD40, tumor necrosis factor receptor superfamily, member 4 (TNFRSF4, best known as OX40) or TNFRSF18 (best known as GITR). The CTLA4-targeting mAb ipilimumab has been approved by the US Food and Drug Administration for use in patients with unresectable or metastatic melanoma in 2011. The therapeutic profile of ipilimumab other CTLA4-blocking mAbs, such as tremelimumab, is currently being assessed in subjects affected by a large panel of solid neoplasms. In the last few years, promising clinical results have also been obtained with nivolumab, a PD-1-targeting mAb formerly known as BMS-936558. Accordingly, the safety and efficacy of nivolumab and other PD-1-blocking molecules are being actively investigated. Finally, various clinical trials are underway to test the therapeutic potential of OX40- and GITR-activating mAbs. Here, we summarize recent findings on the therapeutic profile of immunostimulatory mAbs and discuss clinical trials that have been launched in the last 14 months to assess the therapeutic profile of these immunotherapeutic agents.

Development of ipilimumab: a novel immunotherapeutic approach for the treatment of advanced melanoma

The immunotherapeutic agent ipilimumab has helped address a significant unmet need in the treatment of advanced melanoma. Ipilimumab is a fully human monoclonal antibody that targets cytotoxic T-lymphocyte antigen-4 (CTLA-4), thereby augmenting antitumor immune responses. After decades in which a number of clinical trials were conducted, ipilimumab was the first therapy to improve overall survival in a randomized, controlled phase III trial of patients with advanced melanoma. These results led to the regulatory approval of ipilimumab at 3 mg/kg for the treatment of unresectable or metastatic melanoma. More than 17,000 patients worldwide have received ipilimumab, either as a commercial drug at 3 mg/kg or in clinical trials and expanded access programs at different doses. Consistent with its proposed mechanism of action, the most common toxicities associated with ipilimumab therapy are inflammatory in nature. These immune-related adverse events were mostly reversible when effective treatment guidelines were followed. Importantly, long-term follow-up of patients who received ipilimumab in a phase III trial showed that 24% survived at least two years, and in phase II studies, a proportion of patients survived at least five years. Evaluation of ipilimumab is ongoing in the adjuvant setting for melanoma, and for advanced disease in nonsmall cell lung, small cell lung, prostate, ovarian, and gastric cancers.