Open Label Study of Single Agent Oral RG7388 in Patients With Polycythemia Vera and Essential Thrombocythemia
Open Label Study of Single Agent Oral RG7388 in Patients With Polycythemia Vera and Essential Thrombocythemia
This research looks at two conditions, Essential Thrombocythemia (ET) and Polycythemia Vera
 (PV). ET causes people to produce too many blood cells called platelets and PV causes too
 many platelets and red blood cells to be made. Platelets are particles which circulate in the
 blood stream and normally prevent bleeding and bruising. Having too many platelets in the
 blood increases the risk of developing blood clots, which can result in life threatening
 events like heart attacks and strokes. When the number of red blood cells is increased in PV
 this will slow the speed of blood flow in the body and increase the risk of developing blood
 clots.

 The purpose of Part A of this study is to test the safety and tolerability of drug RG7388
 patients and identify the recommended phase II dose in a single agent dose escalation study.
 The investigators want to find out what effects, good and/or bad it has on the disease.

 The purpose of Part B of this study is to test the safety and tolerability of the combination
 of RG7388 and Pegylated Interferon Alfa-2a or Pegasys in PV/ET patients from Part A who did
 not achieve at least a partial response by the end of three cycles of single agent RG7388.

 Essential Thrombocythemia (ET) and Polycythemia Vera (PV) have been difficult diseases to
 treat. RG7388 is a selective inhibitor of the p53-MDM2 binding that frees p53 from negative
 control and activates the p53 pathway in cancer cells, leading to cell cycle arrest and
 apoptosis in vitro and in vivo. It has been used to treat solid tumors and Acute Myelogenous
 Leukemia (AML) in clinical trials. Pegasys is a drug that is the standard of care for
 patients who have Chronic Hepatitis B (CHB).

 RG7388 is a drug that is not yet approved by the Federal Drug Administration (FDA) for the
 treatment of patients with essential thrombocythemia or polycythemia vera. Pegasys is a drug
 that is approved by the FDA for the treatment of CHB. The use of RG7388 alone and in
 combination with Pegasys is experimental.
The Philadelphia chromosome-negative chronic myeloproliferative neoplasms (MPNs) are a group
 of hematopoietic stem cell malignancies that include polycythemia vera (PV), essential
 thrombocythemia (ET), and primary myelofibrosis (PMF). PV and ET can evolve into
 myelofibrosis, termed post PV/ET MF. ET, PV and PMF have variable tendencies to transform to
 blast phase disease with a dismal prognosis. JAK2V617F is a point activating mutation
 resulting in the constitutive activity of the JAK-STAT pathway within hematopoietic cells in
 approximately 96%, 50%, and 50% of patients with PV, ET, and MF, respectively.

 Polycythemia Vera is characterized by an absolute increase in red cell mass. Patients with PV
 have a median survival if untreated of approximately 18 months from the time of diagnosis and
 treated of approximately 18 years. PV-related symptoms include headache, weakness, dizziness,
 epigastric distress, and pruritus. PV-related signs include hypertension, gout, left upper
 abdominal quadrant pain, high hematocrit, leukocytosis, and thrombocytosis. Major causes of
 reduced survival include thrombosis (29%), bleeding (7%), evolution to myelofibrosis (3%),
 transformation to acute leukemia (23%), and solid tumors (16%). PV patients are stratified
 for risk of thrombosis by age >60 and history of prior thrombotic events. Therapy for low
 risk PV includes low dose aspirin and therapeutic phlebotomy to maintain a hematocrit <45% in
 a man and 42% in a woman. Cardiovascular risk factor modification such as weight loss,
 control of hypertension and hypercholesterolemia, and smoking cessation are also important
 adjunctive approaches to all patients with PV. High risk patients are also treated with
 cytoreductive therapy in the form of hydroxyurea to further reduce the risk of thrombotic
 complications.

 Essential Thrombocythemia is characterized by persistent isolated thrombocytosis and tendency
 for arterial and venous thrombosis. A similar pattern of symptoms as noted above with PV are
 also seen in patients with ET. The median survival of patients with ET is similar to that of
 age and sex matched cohort and in some patients is limited by thrombotic complications (22%),
 evolution to MF (10%), and acute leukemia (2%) (Barbui. J Clin Oncol. 2011; 29(23):3179).
 Risk stratification for occurrence of thrombosis is based on age >60 years and/or history of
 thrombosis. Additionally, cardiovascular risk factors and persistent thrombocytosis >1.5 x
 109/L are believed to influence thrombotic risk and leukemic transformation has been shown to
 be associated with anemia, older age, and leukocytosis. JAK2V617F is present in approximately
 50% of cases and helps establish a diagnosis of a clonal thrombocytosis, and has been shown
 in some studies to predict for a higher risk of thrombosis and potential for transformation
 to PV. Management is aimed at reducing thrombotic risk with the use of low dose aspirin in
 low risk patients (no risk factors) and cytoreductive therapy in high risk patients (at least
 one risk factor). Hydroxyurea, anagrelide, and interferon (IFN) have all been used to
 maintain a platelet count below 400 x 109/L in patients with a history of thrombosis
 (secondary prophylaxis). Currently, hydroxyurea is considered standard of care for high risk
 ET patients based on the results of the PT-1 study which demonstrated superiority of
 hydroxyurea over anagrelide in arterial thrombosis risk reduction and worsening marrow
 reticulin fibrosis in patients receiving anagrelide (Harrison N Engl J Med. 2005;353(1):33).
 Hydroxyurea is associated with a risk of oral and skin ulcers, rash, and unacceptable
 myelosuppression that can sometimes limit use in patients with ET/PV. Additionally, some
 patients are unable to achieve adequate control of blood counts at doses below 2000 mg/daily
 and this has been termed "resistance". Importantly, although a theoretical concern of
 leukemogenic potential of hydroxyurea exists, based on the mechanism of action of this
 chemotherapeutic agent, there are no definitive prospective studies clearly documenting an
 increased risk of leukemic transformation.

 More recently, a renewed interest in interferon-α for the treatment of PV as an alternative
 therapeutic approach has led to the evaluation of pegylated interferon-α 2a (Pegasys, Roche)
 in several phase II studies. Pegasys has an improved toxicity profile over intron-a and can
 be self-administered by the patient on a weekly basis. Currently, Pegasys is being evaluated
 in two large international trials within the myeloproliferative disorder research consortium
 (MPD-RC). The MPD-RC 111 study is a phase II study intended to evaluate the response by
 European LeukemiaNet (ELN) criteria in patients with high risk ET/PV who are intolerant or
 resistant to hydroxyurea therapy treated with Pegasys. In addition, patients with documented
 JAK2V617F and splanchnic vein thrombosis are also eligible for this clinical trial. MPD-RC
 112 is a phase III study for newly diagnosed high risk PV/ET patients in which patients are
 randomized to either Pegasys or hydroxyurea with a primary endpoint of response rate
 comparison between the two treatment arms.

 The use of intron-a (rIFN-α) and Pegasys has been extensively studied in patients with PV and
 reported rates of discontinuation in the first year of therapy range from 14-40%. Objective
 hematologic responses are seen in approximately 80% of treated patients and achievement in
 complete phlebotomy free state in 60% of PV patients. Trials of Pegasys in the treatment of
 PV have further demonstrated major molecular responses of 19% and complete eradication of
 JAK2V617F in 14-24% of patients. Although hematologic remission can often be achieved within
 months of starting rIFN-α treatment, molecular responses require longer term administration
 and are rarely seen before completion of 12 months of therapy. Additionally, sustained
 molecular remissions have been documented in patients that have discontinued therapy for up
 to 30 months of follow up. In a retrospective review of 118 MPN patients receiving Pegasys
 throughout multiple MPN centers included 55 PV patients with an ORR of 87% (54% CR, 33% PR)
 by ELN criteria [21]. In this review, the most common non-hematologic toxicities were Grade
 1-3 fatigue in 24 patients (20%), Grade 1 liver function test (LFT) elevation in 7 (6%), and
 Grade 1-2 skin/allergic reaction in 6 (5%). Adverse effects leading to discontinuation were
 primarily non-hematologic, although one patient (<1%) discontinued Pegasys therapy due to
 Grade 2 anemia.

 Although the biological mechanism of recombinant IFN in the treatment of PV is not completely
 understood, evidence to suggest promotion of immunoregulatory cell function, inhibition of
 angiogenesis, induction of pro-apoptotic gene expression, alteration of the bone marrow
 microenvironment, suppression of hematopoietic progenitor cells, and increase cycling of
 hematopoietic stem cells (HSC) has been reported.

 In the last several years, oral small molecule tyrosine kinase inhibitors of JAK2 have been
 tested in both pre-clinical and clinical trials of patients with MPNs including PV/ET. These
 agents have demonstrated remarkable responses in terms of reduction in splenomegaly and
 correction of leukocytosis, erythrocytosis, and thrombocytosis. However, mature follow up of
 PV patients treated with JAK2 inhibitors evaluating reduction in thrombotic risk and
 evolution to MF is not known. Currently, Ruxolitinib (Jakafi) is being evaluated in a phase
 III study in patients with high risk PV that are refractory/intolerant to hydroxyurea
 [Response trial: NCT01243944].

 The tumor suppressor p53 plays an integral role in the regulation of the cell cycle,
 apoptosis, DNA repair, and senescence. Fifty percent of cancers are found to have
 inactivating mutations of p53. Although, inactivating mutations of p53 are uncommon in the
 chronic phases of MPNs, they increase in frequency in the blast phase of MPNs. The p53
 pathway can also be down-regulated in MPN cells that express wild-type p53 through
 alternative pathways. Over-expression of the ubiquitin ligase murine double minute 2 (MDM2;
 HDM2 in humans) is a regulator of wild type p53 through a variety of different mechanisms.
 MDM2 1) promotes proteosomal degradation and 2) inhibits p53 transcription, and 3) inhibits
 transactivation 4) facilitates export from the nucleus. Inhibition of MDM2 is expected to
 release the negative regulation of p53 and ultimately promote tumor suppressor function. MDM2
 overexpression can be a consequence of gene amplification, increased transcription, and
 increased translation. It has previously been shown that in primary hematopoietic cells from
 patients with JAK2V617F PV, reduced expression of p53 is a result of increased La autoantigen
 expression leading to increased translation of MDM2. It would appear that JAK2V617F induces
 this ribonucleoprotein and furthermore, La protein expression can be down-regulated by in
 vitro JAK2 inhibitor treatment. Lu et al demonstrated increased MDM2 expression and reduced
 p53 levels in JAK2V617F-positive PV CD34+ cells. The physical structure and interaction of
 p53 and MDM2 is known and has allowed for the development of small molecule inhibitors of
 MDM2-p53 interaction. Nutlin-3, a small molecule antagonist of MDM2, was shown to inhibit the
 proliferation of PV CD34+ cells through increased p53 mediated apoptosis. Moreover, in vitro
 combination of low doses of Pegasys with nutlin-3 resulted in selective and significant
 inhibition of JAK2V67F-positive CD34+ PV colony formation compared to normal colony
 formation. Thus, MDM2 appears to be a novel therapeutic target in JAK2V617F-positive PV and
 ultimately may prove to be most effective when used in combination with Pegasys.

 RG7388 is an MDM2-p53 binding cell cycle inhibitor (antiproliferative) and is expected to be
 myelosuppressive at sufficiently high doses. Nonclinical safety findings with RG7388 that may
 have potential clinical relevance include thrombocytopenia and neutropenia, as well as
 general pancytopenia, and effects on liver function parameters.

 Clinical experience to date suggests a dose relationship for RG7388 and gastrointestinal AEs
 with increased incidence of nausea, vomiting, and diarrhea at higher dose levels;
 gastrointestinal prophylaxis with anti-emetics is recommended. Cytopenias, manifesting as
 thrombocytopenia and neutropenia, occurring at higher dose levels appear to be related to
 exposure.

 Iancu-Rubin et al have investigated the biological effect of RG7112 (first generation MDM2
 inhibitor) induced p53-MDM2 disruption on megakaryopoiesis and platelet production in order
 to better elucidate the mechanism of treatment associated thrombocytopenia (ASH 2012). Bone
 marrow derived CD34+ cells exposed to RG7112 for 7 days generated fewer viable cells, fewer
 CFU-MK colonies as compared to untreated cells. Based on these findings, it would appear that
 RG7112 impacts megakaryopoiesis by two potential mechanisms: 1) Impairing the ability of
 CD34+ cells to generate MK precursors due to increased apoptosis; 2) Limiting DNA synthesis
 and polyploidization during the late stages of MK development due to pharmacological
 activation of p53. A combination of these two effects may provide an explanation for
 thrombocytopenia observed in patients receiving this drug and suggests that p53 plays an
 important role in normal human thrombocytopoiesis.

 Study NP27872 is a multi-center, open-label, first-in-human, Phase I dose-escalation study of
 single agent RG7388, a small molecule MDM2 antagonist, administered orally in patients with
 advanced malignancies except leukemia. The first patient received RG7388 on 15 November 2011.
 As of 13 September 2012, 51 patients have been enrolled in the study.

 Evaluable PK data is available for 22 patients in Study NP27872. There has been no evidence
 of significant accumulation (defined as a mean ratio of area under the curve [AUC]τ [on Day
 15 or 5] to AUCinf [on Day 1] > 2) observed in the study thus far, except for one patient who
 exhibited a long half-life (t½) and consequently had an accumulated drug exposure that
 increased 5-fold from Day 1 to Day 5. This was possibly due to concomitant controlled-release
 oxycodone, as opioids are known to cause delayed gastric emptying and decreased intestinal
 motility. In addition, data from the study demonstrate an approximately linear dose-exposure
 (Day 1 maximum plasma concentration [Cmax]) relationship in RG7388 with moderately high
 inter-patient variability without an absorption plateau to date.

 Macrophage inhibitory cytokine (MIC-1, a secreted protein that is strongly induced by
 activated p53) serum levels has been used to assess pharmacodynamic (PD) effects in this
 Phase I study. Analysis of patients on 100 to 800 mg/day of RG7388 showed that the minimum
 level for p53 induction occurs at a dose of 100 mg/day or a corresponding plasma level of 500
 ng/mL of RG7388. Preliminary analysis of PK and safety data showed that there is an apparent
 PK/PD relationship between an AUC per cycle and Cycle 1 platelet nadir.

 At the data cutoff of 13 September 2012, 51 patients with advanced malignancies had received
 R05503781 in Study NP27872. Fifty patients experienced at least 1 adverse event (AE) and 11
 patients experienced at least 1 serious adverse event (SAE).

 Thirteen SAEs in patients (white blood cell count decreased, platelet count decreased, 2
 cases of neutrophil count decreased, febrile neutropenia, 5 cases of thrombocytopenia, 2
 cases of neutropenia, and diarrhea) were considered by the investigator to be probably
 related to study treatment; 4 SAEs (2 cases of febrile neutropenia, urinary tract infection,
 and anemia) were considered possibly related; 1 SAE (lung infection) was considered remotely
 related; and the other 6 SAEs (infection, sciatica, non-cardiac chest pain, dyspnea, wrist
 fracture, and neutropenia) were considered unrelated. Three patients died due to disease
 progression.

 Eleven patients across all groups and schedules had at least 1 event considered a dose
 limiting toxicity (DLT): a treatment-related SAE of Grade 3 febrile neutropenia, a
 treatment-related SAE of Grade 4 febrile neutropenia, a treatment-related SAE of Grade 4
 platelet count decreased, 3 cases of treatment-related SAEs of Grade 4 thrombocytopenia, a
 treatment-related AE of Grade 4 thrombocytopenia, 3 cases of treatment-related AEs of Grade 4
 thrombocytopenia, a treatment-related AE of Grade 4 neutropenia, a treatment-related SAE of
 Grade 4 neutropenia, a treatment-related AE of Grade 3 diarrhea, 2 cases of treatment-related
 AEs of Grade 3 nausea, and a treatment related AE of Grade 3 vomiting. Six patients
 experienced 8 AEs that led to withdrawal from treatment: 1 (Grade 3 AE of cataracts) was
 considered remotely related to study treatment, 4 (Grade 4 AE of thrombocytopenia/Grade 3 SAE
 of febrile neutropenia, Grade 2 AE of neutropenia, Grade 3 SAE of febrile neutropenia) were
 considered possibly related to study treatment, and 3 (Grade 4 SAE of neutropenia, Grade 4
 SAE of thrombocytopenia/Grade 4 SAE of neutrophil count decreased) were considered probably
 related to study treatment.

 RG7388 is representative of an entirely new branch of the nutlin family of MDM2 antagonists
 and the second agent with this mechanism of action sponsored by Roche. As with the lead
 compound (RO5045337), RG7388 binds selectively to the p53 site on the surface of the MDM2
 molecule in vitro with high affinity and can effectively displace p53 from MDM2, leading to
 stabilization and accumulation of p53 protein and activation of the p53 pathway. RG7388 is
 from a different chemical series compared to the lead compound and binds with higher potency
 and selectivity to the MDM2 protein. This follow-on compound has substantially improved
 pharmacological properties. Preclinical models predict superior efficacy of RG7388 in the
 clinic at lower doses and exposures. Compared to the lead molecule, lower variability may be
 seen given that RG7388 does not have significant pH dependent solubility (fasted and
 fed-state simulated intestinal fluid solubilities are similar). RG7388 at 0.3 μM has
 equivalent apoptotic activity to RO5045337 at 10-fold higher (3 μM) concentration and at 25
 mg/kg has equivalent efficacy to RO5045337 at 4-fold higher dose (100 mg/kg) and better
 potency when given once weekly.

 RG7388 exhibits improved in vitro and in vivo potency against tumor cell lines and
 xenografts, improved CYP inhibition profile, and 2.5- to 20-fold lower projected human
 efficacious dose. Preclinical studies have indicated that tumors expressing wild-type p53 may
 respond to this novel therapeutic strategy that releases p53 from MDM2 inhibition, and tumors
 with wild-type p53 and MDM2 over-expression or amplification are likely to be the most
 sensitive. Results from preclinical safety and toxicology studies support further exploration
 of this compound in cancer patients. In view of the existing unmet medical need in advanced
 cancers expressing the above molecular signature, RG7388 is believed to be a promising agent
 that may offer a new therapeutic option.

 The use of Pegasys in combination with other targeted agents for the treatment of PV/ET would
 allow for the administration of lower doses of Pegasys, thereby reducing dose dependent
 toxicities. Preclinical studies by Lu et al. have demonstrated preferential inhibition of PV
 CD34+ cell proliferation and colony formation at subtherapeutic doses of Pegasys in
 combination with Nutlin-3 [33]. Pegasys increases p53 expression through enhanced
 transcriptional activity via the p38 Map kinase pathway and Nutlin-3 prevents p53 degradation
 via interruption of the MDM2-p53 interaction [34]. Due to the common downstream target effect
 of increased tumor suppressor p53 expression with combination Pegasys and Nutlin-3, lower
 doses of each agent can be used together in PV patients. Thus, the use of RG7388 alone or in
 combination with Pegasys would be anticipated to enhance p53 expression by different
 mechanisms and presents a novel approach to the treatment of PV/ET.
Inclusion Criteria:

 (Patient should meet all the criteria)

 -  JAK2V617F-positive PV or JAK2V617F-positive ET (confirmed by WHO diagnostic criteria)

 -  High risk ET/PV [age >60; history of thrombosis] or low risk disease with symptoms
 [recurrent headaches, paresthesias, pruritus]

 -  Previously treated with at least one other agent [hydroxyurea, interferon, anagrelide]
 and determined to be either intolerant/resistant

 -≥18 years of age

 -  Eastern Cooperative Oncology Group (ECOG) Performance status 0-2

 -  Acceptable pre-study organ function during screening as defined as: Total bilirubin ≤
 1.5 times the upper limit of normal (ULN) unless due to Gilbert's disease or
 hemolysis, Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5
 times ULN, Serum creatinine ≤ 1.5 x ULN

 -  Women of childbearing potential and males must agree to use adequate contraception
 (i.e., hormonal or barrier method of birth control; abstinence) prior to study entry
 and for the duration of study participation. Should a female subject become pregnant
 or suspect she is pregnant while participating in this study, she should inform the
 treating physician immediately

 -  Ability to understand and willingness to sign a written informed consent document.

 Exclusion Criteria:

 -  Meets the criteria for post ET/PV MF as defined by the International Working
 Group-Myeloproliferative Neoplasms Research and Treatment (IWG-MRT)

 -  Blast phase disease (>20% blasts in the marrow or peripheral blood)

 -  Acute thrombosis within 3 months of screening

 -  Uncontrolled intercurrent illness including, but not limited to hepatitis, human
 immunodeficiency virus (HIV) - positive subjects receiving combination antiretroviral
 therapy, ongoing or active infection, symptomatic congestive heart failure, unstable
 angina pectoris, ventricular arrhythmia, or psychiatric illness/social situations that
 would limit compliance with study requirements.