Tissue/Site-Agnostic Study of Ribociclib for Tumors With Cyclin D-CDK4/6 Pathway Genomic Alterations: A Phase II, Open-Label, Single-Arm Basket Study.

PURPOSE: As part of the Novartis Signature Program, this study evaluated the efficacy of ribociclib (selective cyclin-dependent kinase 4/6 [CDK4/6] inhibitor) in patients with cyclin D-CDK4/6 pathway-aberrant tumors. METHODS: This was a phase II, single-arm, signal-seeking study in patients with advanced malignancies that had progressed on or after standard treatment. Prior identification of tumor CDK4/6 mutation or amplification, CCND1/3 amplification, or CDKN2A mutation or loss was required. Clinical benefit (defined as the proportion of patients with response or stable disease at ≥ 16 weeks) was the primary end point. RESULTS: From 61 centers in the United States, 106 patients (median age, 62.5 years) were enrolled across multiple malignancies. The patient population was heavily pretreated (median number of prior therapies, three; range, 0 to 19). Median progression-free survival was 1.8 months (95% CI, 1.8 to 1.9). In patients with solid tumors, the clinical benefit rate was 18.1% (n = 19 of 105) and the overall response rate was 2.9% (n = 3 of 105); three partial responses occurred in patients with adenocarcinoma (unknown primary), soft tissue sarcoma, and urothelial carcinoma. No tumor cohort met the prespecified criteria for success. The most common adverse events suspected to be related to treatment were neutropenia (30.2%; decreased neutrophils, 15.1%), fatigue (31.1%), and nausea (29.2%). Fatigue and nausea were typically mild. Only one incident of febrile neutropenia was experienced (grade 3). CONCLUSION: No new or unexpected safety signals were observed in this heavily pretreated patient population. Although responses were seen in tumors with CCND1-CDK4/6 amplifications, the primary end point was not met, suggesting additional evaluation of ribociclib, possibly as combination therapy, is needed.

Signature program: a platform of basket trials.

Investigating targeted therapies can be challenging due to diverse tumor mutations and slow patient accrual for clinical studies. The Signature Program is a series of 8 phase 2, agent-specific basket protocols using a rapid study start-up approach involving no predetermined study sites. Each protocol evaluated 1 agent (buparlisib, dovitinib, binimetinib, encorafenib, sonidegib, BGJ398, ceritinib, or ribociclib) in patients with solid or hematologic malignancies and an actionable mutation. The primary endpoint of each study was the clinical benefit rate (ie, complete or partial response, or stable disease) at 16 weeks. A total of 192 individual sites were opened in the United States, with a median start-up time of 3.6 weeks. The most common tumor types among the 595 treated patients were colorectal (9.2%), non-small cell lung adenocarcinoma (9.1%), and ovarian (8.4%). Frequent genetic alterations were in PIK3CA, RAS, p16, and PTEN. Overall, 30 partial or complete responses were observed with 6 compounds in 16 tumor types. The Signature Program presents a unique and successful approach for rapid signal finding across multiple tumors and allowed various agents to be evaluated in patients with rare alterations. Incorporating these program features in conventional studies could lead to improved trial efficiencies and patient outcomes.

Relationship between labile plasma iron, liver iron concentration and cardiac response in a deferasirox monotherapy trial.

The US04 trial was a multicenter, open-label, single arm trial of deferasirox monotherapy (30-40 mg/kg/day) for 18 months. Cardiac iron response was bimodal with improvements observed in patients with mild to moderate initial somatic iron stores; relationship of cardiac response to labile plasma iron is now presented. Labile plasma iron was measured at baseline, six months, and 12 months. In patients having a favorable cardiac response at 18 months, initial labile plasma iron was elevated in only 31% of patients at baseline and no patient at six or 12 months. Cardiac non-responders had elevated labile plasma iron in 50% of patients at baseline, 50% patients at six months, and 38% of patients at 12 months. Risk of abnormal labile plasma iron and cardiac response increased with initial liver iron concentration. Persistently increased labile plasma iron predicts cardiac non-response to deferasirox but labile plasma iron suppression does not guarantee favorable cardiac outcome. Study registered at www.clinicaltrials.gov (NCT00447694).

Follow-up report on the 2-year cardiac data from a deferasirox monotherapy trial.

The trial CICL670AUS04 was a single-arm, open-label study of the cardiac efficacy of 18 months of deferasirox monotherapy [1]. Cardiac response in this study was related to the degree of liver siderosis. Patients with mild to moderate liver siderosis improved their cardiac T2* while more severely siderotic patients did not, regardless of initial cardiac iron burden. In this letter, we report 2-year data in those patients who completed a 6-month extension phase (N 5 10). Cardiac and liver iron improved steadily during the 24-month period, with final cardiac T2* and LIC improving 37% and 27%, respectively, in this cohort. Serum ferritin and LVEF were not statistically different at anytime-point. When the extension phase (18-24 months) was considered in isolation, serum ferritin, liver iron concentration, and left ventricular ejection fraction were nearly identical to 18 month results. Despite this, cardiac T2* continued to trend higher, increasing 12.7% from 9.5 ms to 10.7 ms (P 5 0.06). Thus defersirox continued to demonstrate cardiac efficacy in patients with mild to moderate hepatic siderosis throughout 2 years of therapy.

The effect of deferasirox on cardiac iron in thalassemia major: impact of total body iron stores.

We present results from a prospective, multicenter, open-label, single-arm study evaluating response of cardiac and liver iron to deferasirox therapy for 18 months. Twenty-eight patients with abnormal T2* and normal left ventricular ejection fraction were enrolled from 4 US centers. All patients initially received deferasirox doses of 30 to 40 mg/kg per day. Patients were severely iron overloaded: mean liver iron concentration (LIC) 20.3 mg Fe/g dry weight, serum ferritin 4417 ng/mL, and cardiac T2* 8.6 ms. In the intent-to-treat population, 48% reached the primary endpoint (cardiac T2* improvement at 18 months, P = not significant). There were 2 deaths: 1 from congestive heart failure and 1 from sepsis. In the 22 patients completing the trial, LIC and cardiac T2* improvements were 16% (P = .06) and 14% (P = .07), respectively. Cardiac T2* improvement (13 patients) was predicted by initial LIC, final LIC, and percentage LIC change, but not initial cardiac T2*. Cardiac iron improved 24% in patients having LIC in the lower 2 quartiles and worsened 8.7% in patients having LIC in the upper 2 quartiles. Left ventricular ejection fraction was unchanged at all time points. Monotherapy with deferasirox was effective in patients with mild to moderate iron stores but failed to remove cardiac iron in patients with severe hepatic iron burdens. This study was registered at www.clinicaltrials.gov as #NCT00447694.

Overexpression of Gsalpha compensates for myocyte loss in diabetic cardiomyopathy.

The stimulatory G protein Gsalpha transmits signals from activated beta-adrenergic receptors via the cyclic AMP-PKA pathway, targeting the key regulatory protein phospholamban. We hypothesized that mice with intrinsic activation of cardiac Gsalpha are resistant to the development of the diabetic cardiomyopathy phenotype. Accordingly, streptozotocin (STZ)-diabetes mellitus was induced in genetically engineered mice with cardiac-specific Gsalpha overexpression and in nontransgenic (NTG) littermates. At 8 weeks, Gsalpha diabetic mice showed no impairment of LV contractility nor increase in myocyte apoptosis, whereas NTG diabetic mice showed a 30% decrease in +dP/dt and -dP/dt with sustained (3-fold) myocyte loss by apoptosis. To assess the level of myocardial reactive oxygen species, we measured malondialdehyde, a surrogate marker of oxidative stress, which was increased in the hearts of NTG and Gsalpha diabetic mice. In addition, chronic hyperglycemia also increased the activity of catalase and superoxide dismutase in the hearts of NTG and Gsalpha diabetic mice. Hearts of NTG diabetic mice, but not Gsalpha mice, showed increased expression of proapoptosis Bax, downregulation in Bcl2, and an increase in the Bax/Bcl2 ratio. Hearts of NTG diabetic mice showed 60% reduction in phosphorylation at the critical Ser16 residue of phospholamban, whereas phosphorylation at Ser16 was restored in hearts of Gsalpha-diabetic mice. We conclude that cardiac-specific overexpression of Gsalpha compensates for the loss of cardiac function in diabetes mellitus.

PKC-{epsilon}-dependent survival signals in diabetic hearts.

Diabetes mellitus is complicated by the development of a primary cardiomyopathy, which contributes to the excess morbidity and mortality of this disorder. The protein kinase C (PKC) family of isozymes plays a key role in the cardiac phenotype expressed during postnatal development and in response to pathological stimuli. Hyperglycemia is an activating signal for cardiac PKC isozymes that modulate a myriad of cell events including cell death and survival. The epsilon-isozyme of the PKC family transmits a powerful survival signal in cardiac muscle cells. Accordingly, to test the hypothesis that endogenous activation of cardiac PKC-epsilon will protect against hyperglycemic cell injury and left ventricular dysfunction, diabetes mellitus was induced using streptozotocin in genetically engineered mice with cardiac-specific expression of the PKC-epsilon translocation activator [psiepsilon-receptors for activated C kinase (psiepsilon-RACK)]. The results demonstrate a striking PKC-epsilon cardioprotective phenotype in diabetic psiepsilon-RACK (epsilon-agonist) mice that is characterized by inhibition of the hyperglycemia apoptosis signal, attenuation of hyperglycemia-mediated oxidative stress, and preservation of parameters of left ventricular pump function. Hearts of diabetic epsilon-agonist mice exhibited selective trafficking of PKC-epsilon to membrane and mitochondrial compartments, phosphorylation/inactivation of the mitochondrial Bad protein, and inhibition of cytochrome c release. We conclude that activation of endogenous PKC-epsilon in hearts of diabetic epsilon-agonist mice promotes the survival phenotype, attenuates markers of oxidative stress, and inhibits the negative inotropic properties of chronic hyperglycemia.

PKCepsilon inhibits the hyperglycemia-induced apoptosis signal in adult rat ventricular myocytes.

Recruitment of the protein kinase C (PKC) family of isozymes is an integral component of the signaling events that direct cardiac phenotype expressed during postnatal development and in response to pathologic stimuli. Hyperglycemia is a potent activating signal for cardiac PKC isozymes and induces the apoptosis program in cardiac muscle cells. To determine whether cardiac PKC isozymes modulate transmission of the hyperglycemia apoptosis signal, we have employed isozyme-specific peptide modulators to selectively inhibit (PKC betaI/betaII, zeta and epsilon) or activate (PKCepsilon). PKC peptides were delivered to primary cultures of serum starved adult rat ventricular myocytes (ARVM), by conjugation to the homeodomain of drosophila antennapedia. As expected, hyperglycemia induced a 35% increase in ARVM apoptosis. Peptide inhibitors of PKC betaI/betaII and zeta blocked transmission of the hyperglycemia apoptosis signal, whereas the isozyme specific inhibitor of PKCepsilon (epsilonV1-2) did not alter the magnitude of glucose-induced ARVM apoptosis. Alternatively, the PKCepsilon translocation activator (psi epsilonRACK) abolished hyperglycemia-induced apoptosis, strongly suggesting a cardioprotective role for PKCepsilon in this system. Therefore, we conclude that cardiac PKC isozymes modulate hyperglycemia-induced apoptosis and activation of cardiac PKCepsilon protects ARVM from the hyperglycemia-induced death signal.

IGF-1 inhibits the mitochondrial apoptosis program in mesangial cells exposed to high glucose.

The activated insulin-like growth factor-1 receptor (IGF-1R) protects cells from a wide range of apoptotic stimuli. Hyperglycemia promotes the intracellular generation of superoxide anion and hydrogen peroxide, both of which have been linked to the activation of the mitochondrial apoptosis program. Here, we report for the first time that ligand activation of the IGF-1R protects normal human mesangial cells and SV40 murine mesangial cells from the glycol-oxidant-induced apoptosis program. The IGF-1R antiapoptosis program was dependent on the recruitment of both Akt/PKB and the ERK subfamily of mitogen-activated protein kinases. IGF-1 treatment also protected the redox potential of mesangial cells maintained at high ambient glucose concentration, by inhibiting the generation of reactive oxygen intermediates and preserving mitochondrial transmembrane potential. IGF-1R survival signals targeted the Bcl-2 family of proteins to protect against glucose-induced apoptosis and oxidative stress. IGF-1-treated cells exhibited a decrease in the Bax/Bcl-2 ratio; increased phosphorylation/inactivation of Bad at Ser112 and Ser136; inhibition of cytochrome c release; perturbations directionally opposed to the initiation of the apoptosis program. In addition, we demonstrate IGF-1R-activated ERK signaling modules phosphorylate Ser112 of the mitochondrial Bad protein, establishing a direct link between surface IGF-1R and the survival program in mitochondria. Our findings indicate that in mesangial cells maintained at high ambient glucose concentration, IGF-1 activates a survival program that maintains the integrity of mitochondria and prevents the expression of the genetic program for apoptosis.

High glucose promotes mesangial cell apoptosis by oxidant-dependent mechanism.

Reactive oxygen species are recognized as important mediators of biological responses. Hyperglycemia promotes the intracellular generation of superoxide anion and hydrogen peroxide. In several cell lines, oxidant stress has been linked to the activation of death programs. Here, we report for the first time that high ambient glucose concentration induces apoptosis in murine and human mesangial cells by an oxidant-dependent mechanism. The signaling cascade activated by glucose-induced oxidant stress included the heterodimeric redox-sensitive transcription factor NF-kappaB, which exhibited an upregulation in p65/c-Rel binding activity and suppressed binding activity of the p50 dimer. Recruitment of NF-kappaB and mesangial cell apoptosis were both inhibited by antioxidants, implicating oxidant-induced activation of NF-kappaB in the transmission of the death signal. The genetic program for glucose-induced mesangial cell apoptosis was characterized by an upregulation of the Bax/Bcl-2 ratio. In addition, phosphorylation of the proapoptotic protein Bad was attenuated in mesangial cells maintained at high-glucose concentration, favoring progression of the apoptotic process. These perturbations in the expression and phosphorylation of the Bcl-2 family were coupled with the release of cytochrome c from mitochondria and caspase activation. Our findings indicate that in mesangial cells exposed to high ambient glucose concentration, oxidant stress is a proximate event in the activation of the death program, which culminates in mitochondrial dysfunction and caspase-3 activation, as the terminal event.