The following table summarizes key information about our most advanced programs:
A Scientific Overview
EZH2 acts as an epigenetic writer and normally regulates gene expression by placing one or more methyl groups on a histone protein, leading to the suppression of gene expression programs. While this effect of EZH2 on gene expression is a normal part of cellular development, some cancers depend on an abnormal pattern of gene expression and re-direct EZH2 to genes that become abnormally repressed. Cancer cells with these abnormal gene expression programs may be more resistant to anti-cancer therapies.
Abnormal EZH2 function has been implicated in cancer in a number of ways:
- Cancer genetics: mutations in the gene encoding EZH2 result in the altered enzymatic activity of EZH2, and cancer cells become dependent on this abnormal activity for tumor growth. Alternatively, mutations in other epigenetic regulators can change the genes expressed by cancer cells and indirectly create a dependence on EZH2 for cancer cell growth;
- Acquired drug resistance: therapeutic agents promote EZH2-mediated gene silencing that may lead to acquired resistance to these agents; and
- Immune suppression: EZH2-mediated reprogramming of immune cells within the tumor (e.g., T-cells) and tumor cells to create an immune-suppressive tumor microenvironment.
There is a strong association between EZH2 expression and disease progression in metastatic castration-resistant prostate cancer (mCRPC), and a therapeutic approach that targets EZH2 may result in better outcomes than those achieved with approved therapeutic agents that treat mCRPC.
In prostate cancer, the androgen receptor is a key regulator of gene expression and acts as the mediator of androgen signaling in prostate cells. The AR signaling pathway is the primary pathway used by prostate cancer cells to promote tumor growth. We believe that EZH2, by suppressing certain gene sets, enhances AR signaling, which can lead to increased tumor growth. In preclinical studies, we observed enhanced gene expression changes in prostate cancer cells treated with a combination of enzalutamide and CPI-1205 as compared to enzalutamide treatment alone. This corroborates our hypothesis that EZH2 functionally cooperates with androgen receptor signaling to promote prostate cancer growth.
We also believe that EZH2 is utilized by prostate cancer cells to establish resistance to ARS inhibitors. We have observed in preclinical studies that EZH2 inhibitors, such as CPI-1205, in combination with ARS inhibitors synergistically killed tumor cells and demonstrated activity in models that are resistant to ARS inhibitors.
EZH2 also plays a critical role in immune cell function and helps to define the state of certain immune cells. EZH2 is required for the activation of T-cells to support differentiation into T regulatory cells, or T-reg cells, which are T-cells that suppress an immune response. Alternatively, EZH2 is required to weaken T-effector cells, which are T-cells that execute an immune response. In mouse models, the genetic loss of EZH2 in T-reg cells rendered mice immune to tumors. We have observed that blocking of EZH2 activity inactivated T-reg cells and stimulated T-effector cell function in vitro, and CPI-1205 resulted in the inhibition of tumor growth in vivo.
CPI-1205, one of our two lead product candidates, is a small molecule designed to promote anti-tumor activity by specifically inhibiting EZH2, an enzyme that suppresses target gene expression. In preclinical studies, we observed that CPI-1205 inhibited tumor growth as a single agent and synergistically enhanced the efficacy of cancer therapies, including ARS inhibitors in a prostate cancer model and immune checkpoint inhibitors in other solid tumor models. Based on these observations and the limited options for patients who progress on ARS inhibitors or immune checkpoint inhibitors, we have prioritized clinical development of CPI-1205 as a combination therapy with ARS inhibitors in prostate cancer and immune checkpoint inhibitors in solid tumors.
We are currently conducting the ProSTAR trial, which is an open-label Phase 1b/2 clinical trial of CPI-1205 for the treatment of metastatic castration-resistant prostate cancer (mCRPC) in combination with enzalutamide or abiraterone acetate, which are second-generation ARS inhibitors. We previously completed a Phase 1 clinical trial of CPI-1205 as a monotherapy in patients with relapsed B-cell lymphoma in which CPI-1205 demonstrated clinical activity and was well tolerated.
We believe that EZH2 has a role in immune cell activity, and we have initiated the ORIOn-E trial, which is a Phase 1b/2 clinical trial of CPI-1205 for the treatment of solid tumors in combination with ipilimumab (marketed as Yervoy®) or pembrolizumab (marketed as Keytruda®), which are immune checkpoint inhibitors. Disclaimer: CPI-1205 is an investigational therapy and has not been approved by the FDA (or any other regulatory authority). CPI-1205 is not available for use outside of a clinical trial setting.
According to the American Cancer Society, or ACS, prostate cancer is the second most common type of cancer among men in the United States and is the second leading cause of cancer death in this population. In 2018, the ACS estimates that in the United States approximately 165,000 men will be diagnosed with prostate cancer and that there will be approximately 29,000 deaths due to prostate cancer.
We believe that there are approximately 140,000 men in the United States living with castration-resistant prostate cancer and that the majority of those patients will develop mCRPC. Based on third-party data, we estimate that there are approximately 30,000 to 50,000 new mCRPC patients per year in the United States. Most patients progress from earlier prostate cancer stages, while some patients are initially diagnosed with metastatic disease. We believe that most patients with mCRPC receive treatment with at least one ARS inhibitor. According to published literature, approximately 60-80% of patients with mCRPC respond to first-line treatment with either abiraterone acetate or enzalutamide with nine to 15 months of progression-free survival. Of those who have a PSA response, a large majority eventually develop resistance to ARS inhibitors. Resistance mechanisms to ARS inhibitors include AR amplification and overexpression and circulating androgen receptor splice variant-7, or ARV7, which is a constitutively active version of the AR that is no longer inhibited by ARS inhibitors. ARV7 is a marker for aggressive mCRPC.
If patients with mCRPC have disease progression after treatment with a second-generation ARS inhibitor, they may be treated with either chemotherapy or a different second-generation ARS inhibitor. Experts that treat mCRPC patients estimated that only 10-30% of patients will respond to the second-line treatment with a different ARS inhibitor and that the response achieved is typically less than half as durable, with three to six months of progression-free survival, as compared to the response observed with first-line ARS inhibitor treatment. After treatment and progression with a second ARS inhibitor or chemotherapy, patients with mCRPC have very limited treatment options other than pain management and other palliative care options. We believe patients who have received either abiraterone acetate or enzalutamide as a first- or second-line therapy would be candidates for combination therapy with these therapies and CPI-1205.
We designed CPI-0209, our second-generation EZH2 inhibitor, to achieve comprehensive coverage of EZH2, which we believe will enable us to expand the addressable patient populations beyond those that have been targeted by first-generation EZH2 inhibitors. We are currently advancing CPI-0209 in IND-enabling studies and plan to initiate a Phase 1 clinical trial in solid tumors and/or hematological malignancies in 2019. Disclaimer: CPI-0209 is an investigational therapy and has not been approved by the FDA (or any other regulatory authority). CPI-0209 is not available for use outside of a clinical trial setting.
A Scientific Overview
Abnormal BET function has been implicated in cancer through several means, including chromosomal translocation, gene amplification and overexpression whereby oncogenic and inflammatory signals are turned on in cancer cells through altered BET activity.
Of note, BET proteins control the expression of the target genes of NF-κB, a key immune signaling pathway that is abnormally activated in various diseases, including cancer and immune disorders. NF-κB signaling has been shown to be abnormally high in some hematological malignancies, such as MF and activated B cell-like diffuse large B-cell lymphoma, or ABC-DLBCL. In preclinical studies in MF, animals treated with BET inhibitors alone or in combination with a JAK2 inhibitor displayed a reduction in NF-κB signaling, improvement in bone marrow fibrosis and reduced disease burden.
In addition, BET proteins promote the generation of megakaryocytes from hematopoietic stem cells. Megakaryocytes normally function to produce platelets, which are small blood cells involved in blood clotting. We believe that the blood cells most responsible for bone marrow scarring in MF are dysfunctional megakaryocytes, which produce inflammatory molecules in part through elevated NF-κB signaling.
CPI-0610 is a potent and selective small molecule designed to promote anti-tumor activity by selectively inhibiting the function of BET proteins to decrease the expression of abnormally expressed genes in cancer. Our epigenetics platform includes a deep understanding of the biological contexts in which BET proteins operate, including cancer pathways that are highly sensitive to CPI-0610. A combination of our preclinical studies, as well as translational insights from our first-in-human study of CPI-0610, led us to prioritize the clinical development of CPI-0610 in myelofibrosis (MF).
We are currently enrolling patients in an open-label Phase 2 clinical trial of CPI-0610 as a second-line treatment of MF, a progressive hematological cancer, as a monotherapy and in combination with ongoing ruxolitinib treatment. We are enrolling patients who have been previously treated with ruxolitinib or an investigational JAK1/JAK2 inhibitor. There are no approved products for patients with MF whose disease progresses after treatment with ruxolitinib. Preliminary data to date from this Phase 2 trial suggest CPI-0610 has the potential to offer meaningful benefits beyond the current standard of care.
CPI-0610 was well-tolerated across three Phase 1 clinical trials of hematologic malignancies. We identified the maximum tolerated dose and observed CPI-0610-mediated pharmacodynamic changes and clinical activity at a range of doses below the maximum tolerated dose. Disclaimer: CPI-0610 is an investigational medicine and has not been approved by the FDA (or any other regulatory authority). CPI-0610 is not available for use outside of a clinical trial setting.
Myelofibrosis (MF) is part of a collection of progressive blood cancers known as myeloproliferative neoplasms and is associated with significantly reduced quality of life and shortened survival. As the disease progresses, the bone marrow produces fewer red blood cells, and within one year of diagnosis, the incidence of thrombocytopenia (a condition characterized by low platelet counts in the blood), severe anemia (a condition characterized by low red blood cell counts), and red blood cell transfusion requirements increase significantly. Among other complications, most patients with MF have enlarged spleens, as well as many other physical symptoms, including abdominal discomfort, bone pain and extreme fatigue.
Ruxolitinib, a JAK1/JAK2 inhibitor, is the current standard of care for intermediate- and high-risk MF patients. Ruxolitinib inhibits dysregulated Janus kinase, or JAK, signaling that is associated with MF. There are limited treatment options for patients with MF. Patients with low red blood cell or platelet counts are ineligible to receive ruxolitinib. In addition, we believe that up to 75% of patients will not tolerate treatment with ruxolitinib or will have an insufficient response to treatment within five years of beginning treatment. Patients have poor survival following discontinuation of therapy with ruxolitinib. We believe that CPI-0610 may enhance the activity of ruxolitinib and also may provide a therapeutic option for patients who discontinue or receive lower doses of ruxolitinib.
We believe that at least two-thirds of the 17,000 to 20,000 MF patients in the United States are intermediate- or high-risk patients and are therefore eligible for systemic treatment, including ruxolitinib. Incyte Corporation, which markets ruxolitinib, has estimated that 40% of these eligible patients receive treatment with ruxolitinib. There are no disease-modifying drugs approved for treatment of patients suffering from MF as first or subsequent lines of therapy.
ProSTAR Trial: Phase 1b/2 Clinical Trial in Combination with Second-Generation ARS Inhibitors. We are currently conducting an open-label Phase 1b/2 clinical trial of CPI-1205 in patients with mCRPC who previously progressed on treatment with either abiraterone acetate or enzalutamide. We are aiming to establish safety, pharmacokinetics, pharmacodynamics, maximum tolerated dose and a recommended Phase 2 dose of CPI-1205 with these agents. In this trial, patients who have previously progressed on treatment with abiraterone acetate are treated with a combination of enzalutamide and CPI-1205, and patients who have previously progressed on treatment with enzalutamide are treated with a combination of abiraterone acetate and CPI-1205.
ORIOn-E Trial: Phase 1b/2 Clinical Trial in Combination with Immune Checkpoint Inhibitors. We have also initiated a Phase 1b/2 clinical trial of CPI-1205 in combination with ipilimumab or pembrolizumab for the treatment of patients with solid tumors, who have previously progressed on treatment with an immune checkpoint inhibitor that inhibits programmed death-ligand 1, or PD-L1, or programmed cell death protein 1, or PD-1.
Phase 2 Clinical Trial for CPI-0610. We are evaluating CPI-0610 in an open-label Phase 2 clinical trial as a second-line treatment for MF. In this trial, we are enrolling patients in a combination arm of CPI-0610 with ruxolitinib or in a monotherapy arm. In the combination arm, we are enrolling patients who have disease progression while being treated with ruxolitinib, but who remain on ruxolitinib treatment. In this arm, we add on CPI-0610 to ruxolitinib treatment. In the monotherapy arm, we are enrolling patients who had disease progression despite prior treatment with ruxolitinib and certain patients who are not eligible for treatment with ruxolitinib. We are evaluating safety, pharmacokinetics, reduction in spleen size measured by MRI and palpation, patient-reported symptom improvement and improvements in red blood cell and platelet counts. We also plan to collect and analyze biomarkers to assess molecular features of the biology of BET proteins and myeloid cells, which may allow us to enrich for patients who are most likely to respond to treatment with CPI-0610.
In addition to the programs discussed above, we have a preclinical pipeline focused on cancer- and immuno-epigenetics. We have used our epigenetics platform to validate novel targets and to generate small-molecule inhibitors against these targets that act on tumor or immune cells. We aim to test these molecules in clinical trials in indications with a defined biological rationale utilizing trial designs that are supported by biomarkers for patient enrichment.