First, my apologies for the length of time from my last clinical update. I’m not generally a superstitious person, but I wanted to wait for a few formalities to be addressed before posting.
Previously, I referenced that my next therapy would likely be at Memorial Sloan-Kettering Cancer Center (MSKCC) and include Opdivo® (nivolumab), a form of immunotherapy called a “checkpoint inhibitor.” What is that, you ask? Human cells carry certain proteins on their surface that enable them to escape attack from the body’s immune system. Some cancer cells wear one of those same proteins, called programmed death ligand 1 (PD-L1), which renders the cancer cells invisible to the body’s immune system. Blocking either PD-L1 or its receptor, programmed death 1 (PD-1), appear to be Achilles’ heels for multiple tumor types. Coincidentally, I covered the exciting early developments in the checkpoint inhibitor field in July 2013, which you can read by clicking here.
My concern is that across clinical studies in numerous cancer types, only about 20% of patients receiving checkpoint inhibitors have a durable response. For these patients, the benefits tend to last for years – perhaps even indefinitely. Exciting, yes. But for the other 80% of patients, the results are less dramatic. For example, in the recurrent head and neck cancer study for Opdivo, the median overall survival was 7.5 months for patients that received Opdivo versus 5.1 months for patients that received standard therapy options (cetuximab, methotrexate, or docetaxel). Clearly, Opdivo was superior to standard therapies and definitely worth considering. But the median overall survival is the time period lying at the midpoint of a frequency distribution of observed values, such that there is an equal probability of falling above or below it. The prospect of being in the 80% group with less than a year to live forced me to consider alternatives.
Fortunately, I became aware of a clinical trial for an investigational agent called M7824, a bifunctional fusion protein targeting PD-L1 and TGF-β, that was developed by EMD Serono, the biopharmaceutical division of Merck KGaA, Darmstadt, Germany. M7824 is currently being studied in a Phase 1 trial for patients with advanced solid tumors (ClinicalTrials.gov Identifier: NCT02517398). The principal investigator for the study is James L. Gulley, M.D., Ph.D., F.A.C.P. of the National Institutes of Health, Center for Cancer Research. In addition to his role as Chief of the Genitourinary Malignancies Branch, Dr. Gulley is also Director of the Medical Oncology Service, Office of the Clinical Director. He is an internationally recognized expert in cancer immunotherapy and I’ve had the honor of knowing him professionally for more than a decade – starting back when I was at Cytogen Corp (just an amazing individual and I cannot say enough good things about him!). Other key members of my fabulous team so far include Dr. Julius Strauss, Lead Associate Investigator for the study and Fellow Physician in Oncology at the National Institutes of Health, Andrea D. Burmeister, Physician Assistant, and Elizabeth Lamping RN, BSN, Research Nurse Specialist.
M7824 consists of a fully human monoclonal antibody against PD-L1 plus a transforming growth factor beta (TGF-β)-neutralizing trap component. This means that M7824 should confer all of the benefits of a checkpoint inhibitor against PD-L1, but with the added punch of neutralizing TGF-β. Dual targeting of the PD-L1 and TGF-β pathways makes sense because both are key immune evasion pathways with independent yet complementary functions.
The TGF-β signaling pathway is complex – resulting in either tumor suppressor or tumor-promoting activity depending on the cellular context in which the pathway is active. In advanced disease, the tumor suppressor arm of TGF-β signaling is lost and, instead, tumor cells proliferate. Further, TGF-β overexpression in advanced disease enhances tumor growth, suppresses the immune system, and exacerbates invasive and metastatic tumor cell behavior.
The more I researched TGF-β, the more encouraged I became about enrolling in the M7824 clinical trial – especially given the specific profile of my disease. Recall that I was diagnosed with human papillomavirus “HPV” positive, squamous cell carcinoma (SCC), which is cancer that begins from squamous cells, a type of skin cell. In addition to being one of the main types of skin cancer, cancers that involve the anus, cervix, head and neck, and vagina are also most often SCC.
Only a minority of people exposed to human papillomavirus develop HPV-related cancer, such as oropharyngeal cancer (lucky me!) or cervical cancer. In a paper published December 2014 in Cancer Research, Levovitz et al. demonstrated that genetic variation in immune-related genes is a determinant of susceptibility to oropharyngeal cancer and other HPV-associated cancers, particularly those related to TGF-β signaling. In other words, it is possible that people carrying genotypes with such variants are more likely to have an HPV-positive tumor compared to patients with the wild-type genotype. The likely functional significance of altered TGF-β signaling in HPV-related cancers is further supported by the finding by Levovitz et al. that TGF-β receptor type 1 is significantly overexpressed in both oropharyngeal cancer and cervical cancer.
In a paper published in February 2015 in Cell, Oshimori et al. establish a surprising non-genetic paradigm for TGF-β signaling in fueling heterogeneity in squamous cell carcinoma (SCC) stem cells, tumor characteristics, and drug resistance. Armed with this insight as well as the relevance for HPV-positive cancers, I decided to enroll in the study and passed the screening process.
In December 2016, Dr. Gulley presented preliminary data from the ongoing Phase 1 study of M7824 at the 28th symposium on Molecular Targets and Cancer Therapeutics, also known as the ENA symposium. Early results were encouraging, with M7824 associated with complete (CR) and partial responses (PR) in patients with advanced refractory cancer.
Today is my first one-hour infusion of M7824 and I look forward to reporting on my experience with immunotherapy in subsequent posts. With just a few minutes remaining for the infusion – so far, so good!