Jack W. Singer

Janus kinase-signal transducers and activators of transcription (JAK-STAT) signaling is critical to multiple cellular processes, including survival, differentiation, and proliferation. JAK-STAT signaling dysregulation has been noted in inflammatory disorders, and aberrant JAK2 pathway activation has been implicated in myelofibrosis and polycythemia vera. Moreover, 4 therapeutic JAK2 inhibitors (ruxolitinib, fedratinib, momelotinib, and pacritinib) have either been approved or are in advanced clinical development for myelofibrosis. Although all inhibit JAK2, reports indicate that they also inhibit other kinases. Profiling based solely on in vitro potencies is insufficient to predict the observed clinical effects. To provide further translational insights into clinical outcomes, we compared phenotypic biomarker profiles of ruxolitinib, fedratinib, momelotinib, and pacritinib in the BioMAP^® Diversity PLUS panel of 12 human primary cell systems designed to recapitulate key aspects of tissue and disease states. Biomarker activity profiles that represent mechanistic signatures for each agent were compared with each other and a database of reference benchmark profiles. At clinically relevant concentrations, these agents had distinct biomarker impacts indicating diverse mechanistic signatures, suggesting divergent clinical effects for each agent. They disparately modulated inflammatory cytokine production and immune function. At clinically relevant concentrations, ruxolitinib had the broadest scope of activities across all 12 cellular systems, whereas pacritinib was more specific for the BT system (modelling T cell-dependent B cell activation) and exhibited the strongest inhibition of sIL-17A, sIL-2, and sIL-6. All 4 agents were antiproliferative to B cells, but ruxolitinib and momelotinib were also antiproliferative to T cells. These differential activities likely reflect distinct secondary pharmacology for these agents known primarily as JAK2 inhibitors. The phenotypic analysis reported herein represents key data on distinct modes-of-action that may provide insights on clinical outcomes reported for these agents. Such translational findings may also inform the development of next-generation molecules with improved efficacy and safety.

Pixantrone is an aza-anthracenedione with enhanced, preclinical antitumor activity and reduced cardiotoxicity compared with doxorubicin. We compared the efficacy and toxic effect of CPOP-R (substituting pixantrone for doxorubicin) against CHOP-R in untreated, diffuse large B-cell lymphoma (DLBCL) patients. The primary objective was to demonstrate non-inferiority of CPOP-R by complete response/complete response unconfirmed (CR/CRu) rate. The CR/CRu rate for CPOP-R was 75% versus 84% for CHOP-R. Three-year overall survival was lower for CPOP-R (69% versus 85%) (P = 0.029). Median progression-free survival (PFS) was not reached for CPOP-R and was 40 months for CHOP-R [HR 95% confidence interval (CI) = 1.02 (0.60, 1.76), P = 0.934]. Fewer CPOP-R patients developed congestive heart failure (CHF) (0% versus 6%, P = 0.120), ≥20% declines in ejection fraction (2% versus 17%, P = 0.004), or elevations in troponin-T (P = 0.003). CPOP-R is an active regimen with modestly lower response rates than CHOP-R but similar PFS and event-free survival. This study demonstrates a substantially lower cardiotoxicity of pixantrone compared with doxorubicin when used as first-line therapy in DLBCL.

Cardiotoxicity from the antitumor anthracycline doxorubicin correlates with doxorubicin cardiac levels, redox activation to superoxide anion (O₂^._) and hydrogen peroxide (H₂O₂), and formation of the long-lived secondary alcohol metabolite doxorubicinol. Cardiotoxicity may first manifest during salvage therapy with other drugs, such as the anthracenedione mitoxantrone. Minimal evidence for cardiotoxicity in anthracycline-pretreated patients with refractory-relapsed non-Hodgkin lymphoma was observed with the novel anthracenedione pixantrone. We characterized whether pixantrone and mitoxantrone caused different effects on doxorubicin levels, redox activation, and doxorubicinol formation. Pixantrone and mitoxantrone were probed in a validated ex vivo human myocardial strip model that was either doxorubicin-naïve or preliminarily subjected to doxorubicin loading and washouts to mimic doxorubicin treatment and elimination in the clinical setting. In doxorubicin-naïve strips, pixantrone showed higher uptake than mitoxantrone; however, neither drug formed O₂^._ or H₂O₂. In doxorubicin-pretreated strips, neither pixantrone nor mitoxantrone altered the distribution and clearance of residual doxorubicin. Mitoxantrone showed an unchanged uptake and lacked effects on doxorubicin levels, but synergized with doxorubicin to form more O₂^._ and H₂O₂, as evidenced by O₂^._-dependent inactivation of mitochondrial aconitase or mitoxantrone oxidation by H₂O₂-activated peroxidases. In contrast, pixantrone uptake was reduced by prior doxorubicin exposure; moreover, pixantrone lacked redox synergism with doxorubicin, and formed an N-dealkylated product that inhibited metabolism of residual doxorubicin to doxorubicinol. Redox inactivity and inhibition of doxorubicinol formation correlate with the cardiac safety of pixantrone in doxorubicin-pretreated patients. Redox inactivity in the face of high cardiac uptake suggests that pixantrone might also be safe in doxorubicin-naïve patients.

BACKGROUND: Pixantrone dimaleate (pixantrone) has been shown to have antitumor activity in leukemia and lymphoma in vitro models and to lack delayed cardiotoxicity associated with mitoxantrone in animal models. FND‐R, a combination regimen of fludarabine, mitoxantrone, dexamethasone, and rituximab, has been shown to be an effective regimen for low‐grade lymphomas.METHODS: This dose‐escalation study, with an expansion cohort, was conducted to evaluate the safety and preliminary efficacy of FPD‐R, in which pixantrone was substituted for mitoxantrone in the FND‐R regimen, in patients with relapsed or refractory indolent non‐Hodgkin lymphoma (NHL). Escalated doses of pixantrone were administered to newly enrolled patients on day 2 of each 28‐day cycle of FPD‐R.RESULTS: Twenty‐eight of 29 enrolled patients received at least 1 cycle of FPD‐R (median, 5 cycles). Pixantrone 120 mg/m² was identified as the recommended dose in this regimen. Grade 3‐4 adverse events were primarily hematologic; grade 3‐4 lymphopenia occurred in 89% of patients and leukopenia in 79%. No patients developed congestive heart failure or grade 3‐4 cardiac adverse events. Left ventricular ejection fraction decreases occurred in 8 (29%) patients, and most were grade 1 or 2, transient, and asymptomatic. The overall response rate was 89%. Estimated survival was 96% after 1 year and 92% after 3 years.CONCLUSIONS: The FPD‐R regimen was well‐tolerated and highly active in patients with relapsed or refractory indolent NHL. Cancer 2011;. © 2011 American Cancer Society.

Pixantrone is a potentially more effective, less cardiotoxic alternative to doxorubicin for patients with aggressive non-Hodgkin lymphoma (aNHL). This phase I/II non-comparative study evaluated pixantrone in place of doxorubicin in the standard CHOP regimen (cyclophosphamide, doxorubicin, vincristine, and prednisone), i.e. CPOP (cyclophosphamide, pixantrone, vincristine, and prednisone), in patients with relapsed aNHL who had previously received CHOP ± rituximab. Patients were administered pixantrone on day 1 of each 21-day cycle. Phase I (n = 35) dose escalation from 80 mg/m(2) to 180 mg/m(2) established the phase II (n = 30) dose as 150 mg/m(2). In phase II, 20 patients (67%) received all six planned cycles. The objective response rate was 73%, complete response/complete response unconfirmed (CR/CRu) rate was 47%, and median overall survival was 17.9 months. Myelosuppression was nearly universal. Six patients (20%) developed febrile neutropenia. Overall, left ventricular ejection fraction (LVEF) declines ≥10% occurred in 14 patients; declines seemed transient and unrelated to dose. Symptomatic cardiac failure occurred in four patients; however, pre-existing conditions confounded causality.

Background: In Phase I evaluation of CT-2103 (paclitaxel poliglumex), prolongation of prothrombin time (PT) and activated thromboplastin time (aPTT) was observed, without clinical consequence, with doses 1.3–1.5 times higher than the current clinical dose of 175 mg/m². This Phase I, open-label, nonrandomized pilot study was performed to study the effect of the standard dose regimen on blood coagulation. Methods: Seven previously treated solid tumor patients received CT-2103 175 mg/m² intravenously on day 1 of 21-day cycles for a mean of 5.4 cycles (median 4, range 2–14). Plasma samples were collected for cycle 1 predose and at hours 1, 24, 48, and 72 after the end of administration for drug levels, and for PT and aPTT assays. Results: No coagulopathy-related adverse events were documented. Bleeding time remained normal in the six patients tested, with transient increases in PT and aPTT noted but resolving within 72 hours. Titration studies at 100 µg/mL of CT-2103 (corresponding to the standard clinical dose) prolonged PT and aPTT clotting times, produced a modest dose-dependent reduction of thrombin and factor Xa, and no significant changes in factors IXa, XIa, or XIIa. Two patients achieved stable disease for ≥10 cycles. Conclusion: CT-2103 is associated with transient prolongation of PT and aPTT without clinical sequelae.

Multinuclear platinum complexes are characterized by a peculiar DNA binding mode and higher cytotoxic potency than the mononuclear complexes, and efficacy against a wide range of preclinical tumor models. To reduce the high irreversible plasma protein binding and improve the chemical and metabolic drug stability, novel bis-platinum complexes were designed starting from the parent compound CT-3610. The novel second-generation bis-platinum complexes utilize alkylcarboxylate as leaving groups to improve their pharmacokinetic and pharmacodynamic profiles, thus overcoming the limitations of the previously developed multinuclear compounds. The selected compounds [CT-47518 and CT-47463, respectively (bis-capronate) platinum and (bis-butyrate) platinum], have similar in vitro degradation kinetics in human and murine plasma and, above all, an increased stability when compared to CT-3610, particularly in human plasma. In addition, both compounds exhibited a marked cytotoxic potency as compared with cisplatin and oxaliplatin. Interestingly, they were capable of overcoming resistance mediated by DNA mismatch repair defects in different cellular models. The complexes showed marked antitumor efficacy in Pt-refractory tumor xenografts, with remarkable activity in terms of tumor growth inhibition and tumor growth delay. The improved stability profile in human plasma compared to early bis- and triplatinum complexes together with the marked activity in cellular systems as well as in in vivo models, make CT-47518 and CT-47463 attractive candidates for further development.