Local protein kinase A action proceeds through intact holoenzymes

Hormones can transmit signals through adenosine 3’,5’-monophosphate (cAMP) to precise intracellular locations. The fidelity of these responses relies on the activation of localized protein kinase A (PKA) holoenzymes. Association of PKA regulatory (RII) subunits with A-kinase anchoring proteins (AKAPs) confers location, and catalytic (C) subunits phosphorylate substrates. Single-particle electron microscopy demonstrated that AKAP79 constrains RII-C sub-assemblies within 150 to 250Å of its targets. Native mass spectrometry established that these macromolecular assemblies incorporated stoichiometric amounts of cAMP. Chemical-biology and live-cell imaging techniques revealed that catalytically active PKA holoenzymes remained intact within the cytoplasm. In contrast, little, if any PKA activity was detected in the nucleus. Hence the parameters of anchored PKA holoenzyme action are much more restricted than originally anticipated

Characterisation of haematological profiles and low risk of thromboembolic events with bortezomib in patients with relapsed multiple myeloma

Haematological toxicities and thromboembolic (TE) events are common complications of myeloma therapy. TE risk may be elevated with combination regimens, notably thalidomide/lenalidomide plus high-dose dexamethasone; concomitant erythropoietin appears to further increase the risk with lenalidomide-dexamethasone. We characterised thrombocytopenia and neutropenia in the phase 3 APEX (Assessment of Proteasome Inhibition for Extending Remissions) study of bortezomib versus high-dose dexamethasone in relapsed myeloma, and calculated the incidences of deep-vein thrombosis (DVT)/pulmonary embolism (PE) with: bortezomib or dexamethasone +/- erythropoietin in APEX; bortezomib +/- dexamethasone +/- erythropoietin in two phase 2 studies of relapsed/refractory myeloma. Bortezomib-associated thrombocytopenia and neutropenia were transient, predictable and manageable; mean platelet and neutrophil counts followed a cyclical pattern, and improved over the treatment course. Grade 3/4 thrombocytopenia incidence was higher with bortezomib versus dexamethasone (26%/4% vs. 5%/1%), but significant bleeding events were comparable (4% vs. 5%). DVT/PE incidence was low (<= 3.1%) in all analyses; addition of dexamethasone/erythropoietin did not affect TE risk. In APEX, TE risk appeared lower with bortezomib versus dexamethasone. Bortezomib caused transient and cyclical thrombocytopenia and was not associated with elevated TE risk, alone or with dexamethasone +/- erythropoietin. Preliminary data suggest bortezomib may reduce the thrombogenic potential of combination regimens via inhibition of platelet function or other mechanism-specific effects on coagulation

Local convergence of the symmetric rank-one iteration

SIGLEAvailable from TIB Hannover: RR 1843(95-07) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Efficacy and safety of bortezomib in patients with renal impairment: results from the APEX phase 3 study

Renal impairment is associated with poor prognosis in multiple myeloma (MM). This subgroup analysis of the phase 3 Assessment of Proteasome Inhibition for Extending Remissions (APEX) study of bortezomib vs high-dose dexamethasone assessed efficacy and safety in patients with relapsed MM with varying degrees of renal impairment (creatinine clearance (CrCl) 80 ml min(-1)). Time to progression (TTP), overall survival ( OS) and safety were compared between subgroups with CrCl 50 ml min(-1) (no/mild impairment). Response rates with bortezomib were similar (36-47%) and time to response rapid (0.7-1.6 months) across subgroups. Although the trend was toward shorter TTP/OS in bortezomib patients with severe-to-moderate vs no/mild impairment, differences were not significant. OS was significantly shorter in dexamethasone patients with CrCl 50 ml min(-1) (P = 0.003), indicating that bortezomib is more effective than dexamethasone in overcoming the detrimental effect of renal impairment. Safety profile of bortezomib was comparable between subgroups. With dexamethasone, grade 3/4 adverse events (AEs), serious AEs and discontinuations for AEs were significantly elevated in patients with CrCl 50 ml min(-1). These results indicate that bortezomib is active and well tolerated in patients with relapsed MM with varying degrees of renal insufficiency. Efficacy/safety were not substantially affected by severe-to-moderate vs no/mild impairment

Reversibility of symptomatic peripheral neuropathy with bortezomib in the phase III APEX trial in relapsed multiple myeloma: impact of a dose-modification guideline

The frequency, characteristics and reversibility of bortezomib-associated peripheral neuropathy were evaluated in the phase III APEX (Assessment of Proteasome Inhibition for Extending Remissions) trial in patients with relapsed myeloma, and the impact of a dose-modification guideline on peripheral neuropathy severity and reversibility was assessed. Patients received bortezomib 1.3 mg/m(2) (days 1, 4, 8, 11, eight 21-d cycles, then days 1, 8, 15, 22, three 35-d cycles); bortezomib was held, dose-reduced or discontinued depending on peripheral neuropathy severity, according to a protocol-specified dose-modification guideline. Overall, 124/331 patients (37%) had treatment-emergent peripheral neuropathy, including 30 (9%) with grade >= 3; incidence and severity were not affected by age, number/type of prior therapies, baseline glycosylated haemoglobin level, or diabetes history. Grade >= 3 incidence appeared lower versus phase II trials (13%) that did not specifically provide dose-modification guidelines. Of patients with grade >= 2 peripheral neuropathy, 58/91 (64%) experienced improvement or resolution to baseline at a median of 110 d, including 49/72 (68%) who had dose modification versus 9/19 (47%) who did not. Efficacy did not appear adversely affected by dose modification for grade >= 2 peripheral neuropathy. Bortezomib-associated peripheral neuropathy is manageable and reversible in most patients with relapsed myeloma. Dose modification using a specific guideline improves peripheral neuropathy management without adversely affecting outcome