Avatrombopag, an Alternate Treatment Option to Reduce Platelet Transfusions in Patients with Thrombocytopenia and Chronic Liver Disease-Integrated Analyses of 2 Phase 3 Studies.

AIMS: Thrombocytopenia complicates the management of patients with chronic liver disease (CLD) undergoing invasive procedures with a bleeding risk. Until recently, prophylactic platelet transfusion was the only treatment option, but has significant safety and efficacy limitations. Phase 3 data demonstrated the superiority of avatrombopag to placebo in reducing platelet transfusions for bleeding, supporting its recent approval. METHODS: Integrated analyses of pooled data (N = 435) from two randomized, double-blind, placebo-controlled, phase 3 studies assessed the original efficacy endpoints. Additional analyses included subgroup analyses, alternate Baseline platelet count definitions, and another efficacy endpoint. RESULTS: Avatrombopag was superior to placebo in increasing patients not requiring a platelet transfusion or rescue procedure, those achieving a platelet count ≥50 × 109/L on Procedure Day, and the change in platelet counts from Baseline. The avatrombopag treatment effect was consistently positive across clinically important disease and Baseline clinical characteristic subgroups, and using alternate Baseline platelet count cohort definitions. Similarly, more avatrombopag-treated patients achieved ≥50 × 109/L platelets with an increase of ≥20 × 109/L from Baseline. The incidence and severity of adverse events were similar between avatrombopag and placebo. Further, safety data demonstrated a low risk for thromboembolic events and hepatotoxicity. CONCLUSION: These integrated analyses confirmed the superiority of avatrombopag to placebo in reducing platelet transfusions or rescue procedures for bleeding in patients with thrombocytopenia and CLD scheduled to undergo an invasive procedure, and its tolerable safety profile. Importantly, these data warrant reconsideration of clinical decision making regarding the need to treat thrombocytopenia in patients with CLD. This trial was registered with NCT01972529 and NCT01976104.

Avatrombopag, an oral thrombopoietin receptor agonist: results of two double-blind, dose-rising, placebo-controlled Phase 1 studies.

Avatrombopag is an oral thrombopoietin receptor agonist that has been recently approved for treating thrombocytopenia in chronic liver disease patients needing invasive procedures. Clinical trials supporting this new treatment were guided by two double-blind, dose-rising, placebo-controlled Phase 1 studies in healthy adults reported here that assessed safety, tolerability and pharmacokinetic profile of avatrombopag, and its effect on platelet counts. Subjects were randomised (2:1) in the single-dose study (N = 63) to avatrombopag (1, 3, 10, 20, 50, 75 and 100 mg) or placebo, and in the multiple-dose study (N = 29) to avatrombopag (3, 10 and 20 mg) or placebo daily for 14 days. There were no serious adverse events (AEs), dose-limiting toxicities, deaths, AEs causing withdrawal, thromboses or liver function abnormalities. In both studies, avatrombopag peak concentration and exposure increased proportionally relative to dose; half-life was 18-21 h and independent of dose, supporting once-daily dosing. Effects on platelet counts depended on dose, concentration and treatment duration. Platelet count increases began 3-5 days post-administration, with maximum changes of >370 × 109 /l over baseline with 20 mg daily after 13-16 days. These data support continued development of avatrombopag for treatment of other thrombocytopenic conditions and provide important guidance for the haematologist in the use of this new thrombopoietin receptor agonist.

Phase 3 randomised study of avatrombopag, a novel thrombopoietin receptor agonist for the treatment of chronic immune thrombocytopenia.

Avatrombopag, an oral thrombopoietin receptor agonist, was compared with placebo in a 6-month, multicentre, randomised, double-blind, parallel-group Phase 3 study, with an open-label extension phase, to assess the efficacy and safety of avatrombopag (20 mg/day) in adults with chronic immune thrombocytopenia (ITP) and a platelet count <30 × 109 /l (ClinicalTrials.gov identifier NCT01438840). The primary endpoint was the cumulative number of weeks of platelet response (platelet count ≥50 × 109 /l) without rescue therapy for bleeding; secondary endpoints included platelet response rate at day 8 and reductions in the use of concomitant medications. Amongst the 49 patients randomised, avatrombopag (N = 32) was superior to placebo (N = 17) in the median cumulative number of weeks of platelet response (12·4 vs. 0·0 weeks, respectively; P < 0·0001). At day 8, a greater platelet response rate was also observed for patients treated with avatrombopag compared with placebo (65·63% vs. 0·0%; P < 0·0001), and use of concomitant ITP medications was also reduced amongst patients receiving avatrombopag. The safety profile of avatrombopag was consistent with Phase 2 studies; the most common adverse events were headache and contusion. Overall, avatrombopag was well tolerated and efficacious for the treatment of chronic ITP.

Avatrombopag Before Procedures Reduces Need for Platelet Transfusion in Patients With Chronic Liver Disease and Thrombocytopenia.

BACKGROUND & AIMS: Patients with thrombocytopenia and chronic liver disease (CLD) may require platelet transfusions before scheduled procedures to decrease risk of bleeding. We performed 2 randomized, placebo-controlled, phase 3 trials in patients with thrombocytopenia and CLD undergoing scheduled procedures to evaluate the safety and efficacy of avatrombopag in increasing platelet counts in this patient population. METHODS: In the ADAPT-1 and ADAPT-2 studies, adults with thrombocytopenia and CLD (n = 231 and n = 204, respectively) were in 1 of 2 cohorts according to their baseline platelet count (below 40 × 109/L or 40 to below 50 × 109/L) and within each cohort were randomized (2:1) to receive 5 daily doses of avatrombopag (60 mg if baseline platelet count below 40 × 109/L or 40 mg if 40 to below 50 × 109/L) or placebo. ADAPT-1 was conducted at 75 study sites in 20 countries, from February 2014 through January 2017, and ADAPT-2 was conducted at 74 sites in 16 countries, from December 2013 through January 2017. The primary endpoint was the proportion of patients not requiring platelet transfusions or rescue procedures for bleeding up to 7 days after a scheduled procedure. RESULTS: In the ADAPT-1 study, 65.6% of patients who received 60 mg avatrombopag and 88.1% of patients who received 40 mg avatrombopag met the primary endpoint compared with 22.9% and 38.2% of patients receiving placebo, respectively (P < .0001 for both). In the ADAPT-2 study, 68.6% of patients who received 60 mg avatrombopag and 87.9% of patients who received 40 mg avatrombopag met the primary endpoint compared with 34.9% and 33.3% of patients who received placebo, respectively (P < .001 for both). Avatrombopag led to a measured increase in platelet counts and increased the proportion of patients who achieved the target platelet count ≥ 50 × 109/L on procedure day vs placebo. The incidence and severity of adverse events were similar for the avatrombopag and placebo groups and were consistent with those expected in the CLD population. CONCLUSIONS: In 2 phase 3 randomized trials, avatrombopag was superior to placebo in reducing the need for platelet transfusions or rescue procedures for bleeding in patients with thrombocytopenia and CLD undergoing a scheduled procedure. ClinicalTrials.gov nos.: NCT01972529 and NCT01976104.

Ferumoxytol versus iron sucrose treatment: a post-hoc analysis of randomized controlled trials in patients with varying renal function and iron deficiency anemia.

BACKGROUND: Iron deficiency anemia is highly prevalent in patients with chronic kidney disease and is often treated with intravenous iron. There are few trials directly comparing the safety and efficacy of different intravenous iron products. METHODS: This post-hoc analysis pooled data from 767 patients enrolled in two randomized, controlled, open-label trials of similar design comparing the treatment of iron deficiency anemia with ferumoxytol and iron sucrose across patients with all stages of renal function. One trial was conducted in adults with CKD either on or not on dialysis and the second in adults with IDA of any underlying cause and a history of unsatisfactory oral iron therapy or in whom oral iron could not be used who had normal to no worse than moderately impaired renal function. Patients were categorized by chronic kidney disease stage (i.e., estimated glomerular filtration rate), and the primary efficacy endpoint was the mean change in hemoglobin from Baseline to Week 5. RESULTS: The overall incidence of adverse events was numerically lower in ferumoxytol-treated patients compared to those treated with iron sucrose (42.4 vs. 50.2 %, respectively); the incidence of treatment-related adverse events was generally similar between the two treatment groups (13.6 vs. 16.0 %, respectively). Adverse events of Special Interest (i.e., hypotension, hypersensitivity) occurred at lower rates in those treated with ferumoxytol compared to those treated with iron sucrose (2.5 vs. 5.3 %, respectively). Overall, mean hemoglobin increased in both treatment groups, regardless of degree of renal insufficiency, although greater increases were seen among those with less severe kidney damage. Mean increases in hemoglobin from Baseline to Week 5 were significantly greater with ferumoxytol than with iron sucrose treatment in the subgroup with an estimated glomerular filtration rate ≥90 mL/min (Least Squares mean difference = 0.53 g/dL; p < 0.001). There were no other consistent, significant differences in hemoglobin levels between treatment groups for the other chronic kidney disease categories except for isolated instances favoring ferumoxytol. CONCLUSIONS: The efficacy and safety of ferumoxytol is at least comparable to iron sucrose in patients with varying degrees of renal function. TRIAL REGISTRATION: (CKD-201; ClinicalTrials.gov identifier: NCT01052779; registered 15 January, 2010), (IDA-302; ClinicalTrials.gov identifier: NCT01114204; registered 29 April, 2010).

Ferumoxytol versus placebo in iron deficiency anemia: efficacy, safety, and quality of life in patients with gastrointestinal disorders.

INTRODUCTION: Iron deficiency anemia (IDA) is common in patients with gastrointestinal (GI) disorders and can adversely affect quality of life. Oral iron is poorly tolerated in many patients with GI disorders. Ferumoxytol is approved for the intravenous treatment of IDA in patients with chronic kidney disease. This study aimed to evaluate the efficacy and safety of ferumoxytol in patients with IDA and concomitant GI disorders. PATIENTS AND METHODS: This analysis included 231 patients with IDA and GI disorders from a Phase III, randomized, double-blind, placebo-controlled trial evaluating ferumoxytol (510 mg ×2) versus placebo in patients who had failed or were intolerant of oral iron therapy. The primary study end point was the proportion of patients achieving a ≥20 g/L increase in hemoglobin (Hgb) from baseline to Week 5. Other end points included mean change in Hgb, proportion of patients achieving Hgb ≥120 g/L, mean change in transferrin saturation, and patient-reported outcomes (PROs). RESULTS: Significantly more patients with IDA receiving ferumoxytol achieved a ≥20 g/L increase in Hgb versus placebo (82.1% vs 1.7%, respectively; P<0.001). Mean increase in Hgb (28.0 g/L vs -1.0 g/L, respectively; P<0.001) significantly favored ferumoxytol treatment. Ferumoxytol-treated patients demonstrated significantly greater improvements than placebo-treated patients relative to their very poor baseline PRO scores posttreatment, including improvements in the Functional Assessment of Chronic Illness Therapy-Fatigue questionnaire and various domains of the 36-Item Short-Form Health Survey. Ferumoxytol-treated patients had a low rate of adverse events. CONCLUSION: In this study, ferumoxytol was shown to be an efficacious and generally well-tolerated treatment option for patients with IDA and underlying GI disorders who were unable to use or had a history of unsatisfactory oral iron therapy.

Pharmacokinetics, metabolism, and excretion of (14)C-labeled belinostat in patients with recurrent or progressive malignancies.

BACKGROUND: Belinostat, a potent pan-inhibitor of histone deacetylase (HDAC) enzymes, is approved in the United States (US) for relapsed/refractory peripheral T-cell lymphoma. In nonclinical studies, bile and feces were identified as the predominant elimination routes (50-70%), with renal excretion accounting for ~30-50%. A Phase 1 human mass balance study was conducted to identify species-dependent variations in belinostat metabolism and elimination. METHODS: Patients received a single 30-min intravenous (i.v.) infusion of (14)C-labeled belinostat (1500 mg). Venous blood samples and pooled urine and fecal samples were evaluated using liquid chromatography-tandem mass spectroscopy for belinostat and metabolite concentrations pre-infusion through 7 days post-infusion. Total radioactivity was determined using liquid scintillation counting. Continued treatment with nonradiolabled belinostat (1000 mg/m(2) on Days 1-5 every 21 days) was permitted. RESULTS: Belinostat was extensively metabolized and mostly cleared from plasma within 8 h (N = 6), indicating that metabolism is the primary route of elimination. Systemic exposure for the 5 major metabolites was >20% of parent, with belinostat glucuronide the predominant metabolite. Mean recovery of radioactive belinostat was 94.5% ± 4.0%, with the majority excreted within 48 and 96 h in urine and feces, respectively. Renal elimination was the principal excretion route (mean 84.8% ± 9.8% of total dose); fecal excretion accounted for 9.7% ± 6.5%. Belinostat was well tolerated, with mostly mild to moderate adverse events and no treatment-related severe/serious events. CONCLUSION: Mass balance was achieved (~95% mean recovery), with metabolism identified as the primary route of elimination. Radioactivity was predominantly excreted renally as belinostat metabolites.

A Phase IIb, Multicenter, Open-Label, Safety, and Efficacy Study of High-Dose, Propylene Glycol-Free Melphalan Hydrochloride for Injection (EVOMELA) for Myeloablative Conditioning in Multiple Myeloma Patients Undergoing Autologous Transplantation.

Autologous stem cell transplantation (ASCT) after high-dose melphalan conditioning is considered a standard of care procedure for patients with multiple myeloma (MM). Current formulations of melphalan (eg, Alkeran for Injection [melphalan hydrochloride]; GlaxoSmithKline, Research Triangle Park, NC, USA) have marginal solubility and limited chemical stability upon reconstitution. Alkeran requires the use of propylene glycol as a co-solvent, which itself has been reported to cause such complications as metabolic/renal dysfunction and arrhythmias. EVOMELA (propylene glycol-free melphalan HCl; Spectrum Pharmaceuticals, Inc., Irvine, CA, USA) is a new i.v. melphalan formulation that incorporates Captisol (Ligand Pharmaceuticals, Inc., La Jolla, CA, USA), a specially modified cyclodextrin that improves the solubility and stability of melphalan and eliminates the need for propylene glycol. This new formulation has been shown to be bioequivalent to Alkeran. EVOMELA (200 mg/m(2)) was administered as 2 doses of 100 mg/m(2) each in a phase IIb, open-label, multicenter study to confirm its safety and efficacy as a high-dose conditioning regimen for patients with MM undergoing ASCT. At 5 centers, 61 patients (26 women) with a median age of 62 years (range, 32-73) were enrolled. All patients achieved myeloablation with a median time of 5 days post-ASCT, and all successfully achieved neutrophil and platelet engraftment with median times of 12 days post-ASCT and 13 days post-ASCT, respectively; treatment-related mortality on day 100 was 0%. Overall response rate (according to independent, blinded review) was high (100%), with an overall complete response rate of 21% (13% stringent complete response; 8% complete response) and overall partial response rate of 79% (61% very good partial response; 18% partial response). The incidence of grade 3 mucositis and stomatitis was low (10% and 5%, respectively) with no grade 4 mucositis or stomatitis reported (graded according to National Cancer Institute Common Terminology Criteria for Adverse Events). Based on investigators' assessment of mucositis using the World Health Organization (WHO) oral toxicity scale, 75% of patients had a shift in mucositis score from WHO grade 0 at baseline to a higher grade on study, of which 13% of patients reported WHO grade 3 as the worst post-treatment mucositis over the course of the study; there were no reports of WHO grade 4 mucositis during the study. This study confirms the efficacy and acceptable safety profile of EVOMELA, a new propylene glycol-free melphalan formulation, as a high-dose conditioning regimen for ASCT in patients with MM.

Belinostat in Patients With Relapsed or Refractory Peripheral T-Cell Lymphoma: Results of the Pivotal Phase II BELIEF (CLN-19) Study.

PURPOSE: Peripheral T-cell lymphomas (PTCLs) represent a diverse group of non-Hodgkin lymphomas with a poor prognosis and no accepted standard of care for patients with relapsed or refractory disease. This study evaluated the efficacy and tolerability of belinostat, a novel histone deacetylase inhibitor, as a single agent in relapsed or refractory PTCL. PATIENTS AND METHODS: Patients with confirmed PTCL who experienced progression after ≥ one prior therapy received belinostat 1,000 mg/m(2) as daily 30-minute infusions on days 1 to 5 every 21 days. Central assessment of response used International Working Group criteria. Primary end point was overall response rate. Secondary end points included duration of response (DoR) and progression-free and overall survival. RESULTS: A total of 129 patients were enrolled, with a median of two prior systemic therapies. Overall response rate in the 120 evaluable patients was 25.8% (31 of 120), including 13 complete (10.8%) and 18 partial responses (15%). Median DoR by International Working Group criteria was 13.6 months, with the longest ongoing patient at ≥ 36 months. Median progression-free and overall survival were 1.6 and 7.9 months, respectively. Twelve of the enrolled patients underwent stem-cell transplantation after belinostat monotherapy. The most common grade 3 to 4 adverse events were anemia (10.8%), thrombocytopenia (7%), dyspnea (6.2%), and neutropenia (6.2%). CONCLUSION: Monotherapy with belinostat produced complete and durable responses with manageable toxicity in patients with relapsed or refractory PTCL across the major subtypes, irrespective of number or type of prior therapies. These results have led to US Food and Drug Administration approval of belinostat for this indication.

Qualitative and quantitative validation of the FACIT-fatigue scale in iron deficiency anemia.

BACKGROUND: Fatigue is a burdensome symptom in iron deficiency anemia (IDA). To capture the severity and impact of fatigue appropriately it must be measured using validated scales. This study evaluated the content validity and psychometric validity of the Functional Assessment of Chronic Illness Therapy - fatigue scale (FACIT-fatigue) in IDA patients. METHODS: Qualitative patient interviews were conducted in the United States to evaluate content validity. The psychometric properties of the FACIT-fatigue scale were investigated using data from a phase 3 clinical trial assessing ferumoxytol in patients with a history of unsatisfactory oral iron therapy or in whom oral iron cannot be used. The statistical analysis assessed the acceptability, reliability, validity and responsiveness of the FACIT-fatigue scale. RESULTS: Qualitative interviews showed that fatigue is a central concern to IDA patients and that the FACIT-fatigue scale sufficiently assessed this construct. Psychometric assessment demonstrated that the FACIT-fatigue scale was stable over time (ICC = 0.87) and internally consistent (α = 0.93). The scale demonstrated convergence with other conceptually relevant scales such as SF-36 Vitality (r = 0.74), and distinguished between known groups [i.e., treatment arms (mean difference (95 % CI) = 3.56 (1.68, 5.43), p <0.001) and high vs. low hemoglobin groups (mean difference (95 % CI) = 5.51 (8.59, 2.44) p <0.001)]. Responsiveness was also demonstrated; significant improvements in FACIT-fatigue scale scores corresponded with significant differences between minimal, moderate, and much improved vitality cohorts (p < 0.05). CONCLUSIONS: This research demonstrated that the FACIT-fatigue scale has sound measurement properties and is an appropriate and interpretable assessment of fatigue among IDA patients with various underlying conditions.

A Phase II trial of Belinostat (PXD101) in patients with relapsed or refractory peripheral or cutaneous T-cell lymphoma.

Belinostat is a pan-histone deacetylase inhibitor with antitumour and anti-angiogenic properties. An open label, multicentre study was conducted in patients with peripheral T-cell lymphoma (PTCL) or cutaneous T-cell lymphoma (CTCL) who failed ≥1 prior systemic therapy and were treated with belinostat (1000 mg/m(2) intravenously ×5 d of a 21-d cycle). The primary endpoint was objective response rate (ORR). Patients with PTCL (n = 24) had received a median of three prior systemic therapies (range 1-9) and 40% had stage IV disease. Patients with CTCL (n = 29) had received a median of one prior skin-directed therapy (range 0-4) and four prior systemic therapies (range 1-9); 55% had stage IV disease. The ORRs were 25% (PTCL) and 14% (CTCL). Treatment-related adverse events occurred in 77% of patients; nausea (43%), vomiting (21%), infusion site pain (13%) and dizziness (11%) had the highest incidence. Treatment-related serious adverse events were Grade 5 ventricular fibrillation; Grade 4 thrombocytopenia; Grade 3 peripheral oedema, apraxia, paralytic ileus and pneumonitis; and Grade 2 jugular vein thrombosis. Belinostat monotherapy was well tolerated and efficacious in patients with recurrent/refractory PTCL and CTCL. This trial was registered at www.clinicaltrials.gov as NCT00274651.

A Phase III, randomized, open-label trial of ferumoxytol compared with iron sucrose for the treatment of iron deficiency anemia in patients with a history of unsatisfactory oral iron therapy.

Iron deficiency anemia (IDA) is the most common form of anemia worldwide. Although oral iron is used as first-line treatment, many patients are unresponsive to or cannot take oral iron. This Phase III, open-label, non-inferiority study compared the efficacy and safety of ferumoxytol, a rapid, injectable intravenous (IV) iron product with low immunological reactivity and minimal detectable free iron, with IV iron sucrose in adults with IDA of any cause. Patients (N = 605) were randomized 2:1 to receive ferumoxytol (n = 406, two doses of 510 mg 5 ± 3 days apart) or iron sucrose (n = 199, five doses of 200 mg on five nonconsecutive days over 14 days) and followed for 5 weeks. Ferumoxytol demonstrated noninferiority to iron sucrose at the primary endpoint, the proportion of patients achieving a hemoglobin increase of ≥2 g dL(-1) at any time from Baseline to Week 5 (ferumoxytol, 84.0% [n = 406] vs. iron sucrose, 81.4% [n = 199]), with a noninferiority margin of 15%. Ferumoxytol was superior to iron sucrose (2.7 g dL(-1) vs. 2.4 g dL(-1) ) in the mean change in hemoglobin from Baseline to Week 5 (the alternative preplanned primary endpoint) with P = 0.0124. Transferrin saturation, quality-of-life measures, and safety outcomes were similar between the two treatment groups. Overall, ferumoxytol demonstrated comparable safety and efficacy to iron sucrose, suggesting that ferumoxytol may be a useful treatment option for patients with IDA in whom oral iron was unsatisfactory or could not be used.

Efficacy and safety of IV ferumoxytol for adults with iron deficiency anemia previously unresponsive to or unable to tolerate oral iron.

Although oral iron is the initial treatment approach for iron deficiency anemia (IDA), some patients fail to respond to or cannot tolerate oral iron. This double-blind safety and efficacy study of the intravenous (IV) iron, ferumoxytol, randomized patients with a history of unsatisfactory oral iron therapy, or in whom oral iron could not be used, to ferumoxytol (n = 609) or placebo (n = 203). The proportion of patients achieving the primary endpoint (hemoglobin increase ≥2.0 g/dL at Week 5) was 81.1% with ferumoxytol versus 5.5% with placebo (P < 0.0001). The mean increase in hemoglobin from Baseline to Week 5, a secondary endpoint (also the alternative preplanned primary efficacy endpoint for other health authorities), was 2.7 versus 0.1 g/dL (P < 0.0001). Achievement of a hemoglobin ≥12 g/dL, time to a hemoglobin increase ≥2.0 g/dL, and improvement in the Functional Assessment of Chronic Illness Therapy Fatigue score also significantly favored ferumoxytol over placebo at Week 5 (P < 0.0001). Ferumoxytol treatment-emergent adverse events were mainly mild to moderate. Ferumoxytol was effective and well tolerated in patients with IDA of any underlying cause in whom oral iron was ineffective or could not be used. This trial was registered at www.clinicaltrials.gov as #NCT01114139.

CI-1033, an irreversible pan-erbB receptor inhibitor and its potential application for the treatment of breast cancer.

The erbB family of cell surface receptor proteins consists of four members, all of which play a role in the development and growth of the normal breast. The activity of this signaling pathway is normally tightly controlled, and dysregulation has been shown to play a significant role in the pathogenesis and progression of breast and other cancers. The potent transforming potential of these receptors is further enhanced by the coexpression of multiple members of this receptor family, which worsens prognosis. Therapeutic blockade of erbB-2 receptor signaling has to date been shown to be effective in only a subset of chemotherapy-resistant breast cancer patients. CI-1033 is a highly potent and selective pan-erbB inhibitor that efficiently blocks signal transduction through all four members of the erbB receptor family. In addition, it covalently binds to these receptors, irreversibility inhibiting them, and thereby provides for prolonged suppression of erbB receptor-mediated signaling. Clinically, it has been shown to have an acceptable side effect profile at potentially therapeutic doses and schedules. Biomarker studies have shown target inhibition in patients, and evidence of antitumor activity has also been observed in phase I studies. Given the broad expression pattern of the erbB family of receptors in solid tumors, and the important proliferative effect of co-expression of multiple erbB receptors, CI-1033, as an irreversible, pan-erbB inhibitor, has the potential to have an important role in the future treatment of breast and other cancers.

CI-1040 (PD184352), a targeted signal transduction inhibitor of MEK (MAPKK).

Several key growth factors, cytokines, and proto-oncogenes transduce their growth- and differentiation-promoting signals through the mitogen-activated protein kinase or extracellular signal-regulated protein kinase (ERK) cascade. Overexpression or constitutive activation of this pathway has been shown to play an important role in the pathogenesis and progression of breast and other cancers, making the components of this signaling cascade potentially important as therapeutic targets. CI-1040 (PD184352) is an orally active, highly specific, small-molecule inhibitor of one of the key components of this pathway (MEK1/MEK2), and thereby effectively blocks the phosphorylation of ERK and continued signal transduction through this pathway. Antitumor activity has been seen in preclinical models with this compound, particularly for pancreas, colon, and breast cancers, which has been shown to correlate with its inhibition of pERK. Clinically, CI-1040 has been shown to be well tolerated in phase I studies, with safety and pharmacokinetic profiles that permit continuous daily dosing. Biomarker studies have shown target inhibition in patients, and antitumor activity has also been observed with a partial response in one patient with pancreatic cancer and stable disease in approximately 25% of phase I patients. Given the central role of the ERK/mitogen-activated protein kinase pathway in mediating growth-promoting signals for a diverse group of upstream stimuli, inhibitors of MEK, as a key central mediator, could have significant clinical benefit in the treatment of breast and other cancers.

Potential benefits of the irreversible pan-erbB inhibitor, CI-1033, in the treatment of breast cancer.

Transmembrane receptor tyrosine kinases have been shown to play an important role in the modulation of growth factor signaling and regulation of key cellular processes. The erbB receptor family is part of the receptor tyrosine kinase superfamily and consists of four members, erbB-1, erbB-2, erbB-3, and erbB-4. A majority of solid tumors express one or more members of this receptor family, and coexpression of multiple erbB receptors leads to an enhanced transforming potential and worsened prognosis. The erbB receptor family has been shown to play an important role in both the development of the normal breast and in the pathogenesis and progression of breast cancer. Receptor overexpression has also been shown to be a negative prognostic indicator and to correlate with both tumor invasiveness and a lack of responsiveness to standard treatment. Clinically, blockade of the erbB-2 receptor has recently been shown to provide benefit in a subset of chemotherapy-resistant breast cancer patients. CI-1033 is an orally available pan-erbB receptor tyrosine kinase inhibitor that, unlike the majority of receptor inhibitors, effectively blocks signal transduction through all four members of the erbB family. In addition, it blocks the highly tumorigenic, constitutively activated variant of erbB-1, EGFRvIII, and inhibits downstream signaling through both the Ras/MAP kinase, and PI-3 kinase/AKT pathways. CI-1033 is also unique in that it is an irreversible inhibitor, thereby providing prolonged suppression of erbB receptor-mediated signaling. Preclinical data have shown CI-1033 to be efficacious against a variety of human tumors in mouse xenograft models, including breast carcinomas. In a phase I study, CI-1033 has been shown to have an acceptable side effect profile at potentially therapeutic dose levels and demonstrates evidence of target biomarker modulation. Antitumor activity has also been observed in this study, including one partial clinical response and stable disease in over 30% of patients, including one patient with heavily pretreated breast cancer. By virtue of its pan-erbB receptor inhibition and potent interruption of downstream mitogenic signaling pathways, CI-1033 may have clinical activity for solid tumors that overexpress one erbB family member, coexpress multiple members of the erbB family, or express a constitutively activated, mutated form of these receptors. Given the important role of the erbB receptor family in the pathogenesis and progression of breast cancer, an irreversible pan-erbB inhibitor like CI-1033 could have an important role to play in the future treatment of breast cancer.