A number of patents and publications are cited herein in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Each of these references is incorporated herein by reference in its entirety into the present disclosure, to the same extent as if each individual reference was specifically and individually indicated to be incorporated by reference.
Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise,” and variations such as “comprises” and “comprising,” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
As used herein, “a,” “an” and “the” include singular and plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “an active agent” or “a pharmacologically active agent” includes a single active agent as well a two or more different active agents in combination, reference to “a carrier” includes mixtures of two or more carriers as well as a single carrier, and the like.
Ranges are often expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment.
Multiple Myeloma
Multiple myeloma is a disseminated malignancy of plasma cells that affects approximately 14,600 new patients each year in the United States. The etiology of this rare blood disease, affecting mainly the middle-aged to elderly population, is largely unknown although genetic predisposition and environmental factors have been implicated. From onset, malignant plasma cells arising from clonal expansion accumulate in the bone marrow, producing abnormally high levels of immunoglobulins. Multiple myeloma is difficult to diagnose early because there may be no symptoms in early stage. Bone pain especially secondary to compression fractures of the ribs or vertebrae is the most common symptom.
Dexamethasone is a commonly used regimen for first-line treatment of this disease. More recently, combinations of vincristine, doxorubicin, and dexamethasone (VAD) have been used to treat multiple myeloma. However, these are not effective long-term treatments. Dexamethasone treatment has a response rate of approximately 25-35%.
In many patients, high-dose chemotherapy supported by autologous stem cell transplantation (ASCT) may prolong event-free survival if the procedure is performed within 12 months of initial diagnosis. However almost all patients receiving high-dose chemotherapy and an autologous peripheral stem cell transplant will ultimately relapse.
Lymphoma
Despite years of research into the development of new methods of treatment, cancers of the lymphatic system, or lymphomas, remain quite common. For example, more than 60,000 people in the United States are diagnosed with lymphoma each year, including more than 55,000 cases of non-Hodgkin's Lymphoma (NHL), and these numbers are constantly increasing. In addition, the prognosis for those affected by these diseases is often poor, as the survival rates for lymphoma patients remain low. Clearly, new methods for treating these diseases are needed.
While traditional treatments for lymphoma typically depend on the type of lymphoma as well as the medical history of the patient, first-line treatment for many lymphomas typically includes chemotherapy. Such chemotherapy will often entail the administration of a “cocktail” of compounds, e.g., the formulation CHOP, which includes cyclophosphamide, doxorubicin, vincristine, and prednisone. In addition, certain first-line cancer treatments also include other forms of cancer therapy, such as radiation therapy.
In many cases, patients respond initially to such first-line treatments, but subsequently suffer a relapse, i.e., a tumor reappears or resumes growing. Following one such relapse, patients are often treated with further chemotherapy, e.g., with CHOP or with other formulations, or, in some cases, the patients are treated with other procedures such as bone marrow transplantation. Again, in many cases, patients initially respond to such additional treatments, but subsequently suffer another relapse. In general, the more relapses a patient suffers, the less agreement there is in the art concerning optimal subsequent treatment. In other cases, a patient fails to respond at all to a treatment, even initially, and is thus said to have a refractory cancer. In such cases as well, little agreement exists in the art regarding optimal subsequent treatment.
Prostate Cancer
Prostate cancer is the most common cancer leading to death among United States men. Its incidence has increased considerably over the past two decades. This cancer is often initially responsive to hormone treatment, but then frequently progresses into a hormone-insensitive state that is not easily treated. Further, once the cancer spreads or metastasizes from the prostate gland to other tissues such as bone marrow, the cancer usually cannot be cured by presently available treatments, which are either too toxic or cannot reach the metastases. There is a dire need for new strategies to treat prostate cancers, including metastasized prostate cancers, with low toxicity.
Ovarian Cancer
Ovarian cancer is the fourth leading cause of cancer deaths among women in the United States and causes more deaths than all other gynecologic malignancies combined.
In the United States, a woman's lifetime risk of developing ovarian cancer is 1 in 70. In 1992, about 21,000 cases of ovarian cancer were reported, and about 13,000 women died from the disease. See, e.g., Chapter 321, Ovarian Cancer, Harrison's Principles of Internal Medicine, 13th ed., Isselbacher et al., eds., McGraw-Hill, New York (1994), pages 1853-1858; and American Cancer Society Statistics, Cancer J. Clinicians, 45:30 (1995). Epithelial ovarian cancer, the most common ovarian cancer, has a distinctive pattern of spread in which cancer cells migrate throughout the peritoneal cavity to produce multiple metastatic nodules in the visceral and parietal peritoneum and the hemidiaphragms. In addition, metastasis can occur to distant sites such as the liver, lung and brain. Early stage ovarian cancer is often asymptomatic and is detected coincidentally by palpating an ovarian mass on pelvic examination. In premenopausal patients, about 95% of these masses are benign. Even after menopause, 70% of masses are benign but detection of any enlargement requires evaluation to rule out malignancy. In postmenopausal women with a pelvic mass, a markedly elevated serum CA-125 level of greater than 65 U/mL indicates malignancy with a 96% positive predictive value. See, e.g., Chapter 321, Ovarian Cancer, Harrison's Principles of Internal Medicine, 13th ed., Isselbacher et al., eds., McGraw-Hill, New York (1994).
Epithelial ovarian cancer is seldom encountered in women less than 35 years of age. Its incidence increases sharply with advancing age and peaks at ages 75 to 80, with the median age being 60 years. The single most important risk factor for this cancer is a strong family history of breast or ovarian cancer. Oncogenes associated with ovarian cancers include the HER-2/neu (c-erbB-2) oncogene, which is overexpressed in a third of ovarian cancers, the fms oncogene, and abnormalities in the p53 gene, which are seen in about half of ovarian cancers. A number of environmental factors have also been associated with a higher risk of epithelial ovarian cancer, including a high fat diet and intake of lactose in subjects with relatively low tissue levels of galactose-1-phosphate uridyl transferase.
The internationally accepted first-line chemotherapy for advanced epithelial ovarian cancer is the combination of carboplatin and paclitaxel. Typical results are median progression-free survival (PFS) of 17-20 months and median survival of 3-5 years. Second-line treatment is determined by duration of remission. If relapse occurs within 6 months of the last treatment, patients are considered “platinum resistant.” Re-treatment with a carboplatin/paclitaxel regimen in these patients is associated with a low response rate (15%) of short duration (3-6 months), and a median survival of approximately 12 months. For this patient population, there is a need for a more effective therapy.
Lung Cancer
Lung cancer is the leading cause of cancer mortality in the United States (“Cancer Facts and Figures 2003,” American Cancer Society). Lung cancer is particularly insidious because symptoms of early-stage, localized disease are nonspecific and are frequently attributed to the effects of smoking. By the time the patient seeks medical attention, the disease is usually advanced so that complete surgical resection is possible in less than 30% of all cases, and the overall 5-year survival rate in less than 15%. See, e.g., “Cancer of the Lung: Cancer Screening and Early Detection,” in Cancer Medicine, 5th Edition, Bast et al. eds., B.C. Decker Inc., Hamilton, Ontario, Canada.
Surgery and radiotherapy may be curative if a cancer is found early, but current drug therapies for metastatic disease are mostly palliative and seldom offer a long-term cure. Even with the new chemotherapies entering the market, improvement in patient survival is measured in months rather than in years, and the need continues for new drugs effective both in combination with existing agents as first line therapy and as second and third line therapies in treatment of resistant tumors.
HDAC Inhibitors
Histones are major protein components of chromatin. The regulation of chromatin structure is emerging as a central mechanism for the control of gene expression. As a general paradigm, acetylation of the c-amino groups of lysine residues in the amino-terminal tails of nucleosomal histones is associated with transcriptional activation, while deacetylation is associated condensation of chromatin and transcriptional repression. Acetylation and deacetylation of histones is controlled by the enzymatic activity of histone acetyltransferases (HATs) and histone deacetylases (HDACs). Several transcription factors including p53 and GATA-1 have also been shown to be substrates for HDACs.
Prototypical HDAC inhibitors, such as the natural products trichostatin A (TSA) and suberoyl hydroxamic acid (SAHA), induce the expression of genes associated with cell cycle arrest and tumor suppression. Phenotypic changes induced by HDAC inhibitors include G1, and G2/ M cell cycle arrest and apoptosis in tumor cells. Antitumor activity has been demonstrated in vivo in animal models with a number of HDAC inhibitors, including PXD-101.
PXD-101 is a potent HDAC inhibitor that belongs to the hydroxymate-type of histone deacetylase inhibitors, which for various members of the group has shown pronounced in vitro and in vivo (pre-clinical and early clinical trials) activity against myeloma and lymphoma.