Preclinical, randomized phase 1, and compassionate use evaluation of REGN4461, a leptin receptor agonist antibody for leptin deficiency

Deficiency in the adipose-derived hormone leptin or leptin receptor signaling causes class 3 obesity in individuals with genetic loss-of-function mutations in leptin or its receptor LEPR and metabolic and liver disease in individuals with hypoleptinemia secondary to lipoatrophy such as in individuals with generalized lipodystrophy. Therapies that restore leptin-LEPR signaling may resolve these metabolic sequelae. We developed a fully human monoclonal antibody (mAb), REGN4461 (mibavademab), that activates the human LEPR in the absence or presence of leptin. In obese leptin knockout mice, REGN4461 normalized body weight, food intake, blood glucose, and insulin sensitivity. In a mouse model of generalized lipodystrophy, REGN4461 alleviated hyperphagia, hyperglycemia, insulin resistance, dyslipidemia, and hepatic steatosis. In a phase 1, randomized, double-blind, placebo-controlled two-part study, REGN4461 was well tolerated with an acceptable safety profile. Treatment of individuals with overweight or obesity with REGN4461 decreased body weight over 12 weeks in those with low circulating leptin concentrations (<8 ng/ml) but had no effect on body weight in individuals with higher baseline leptin. Furthermore, compassionate-use treatment of a single patient with atypical partial lipodystrophy and a history of undetectable leptin concentrations associated with neutralizing antibodies to metreleptin was associated with noteable improvements in circulating triglycerides and hepatic steatosis. Collectively, these translational data unveil an agonist LEPR mAb that may provide clinical benefit in disorders associated with relatively low leptin concentrations.

Endogenous Leptin Concentrations Poorly Predict Metreleptin Response in Patients With Partial Lipodystrophy

CONTEXT

Leptin replacement with metreleptin improves glycemia and hypertriglyceridemia in severely hypoleptinemic patients with generalized lipodystrophy (GLD), but its effects are variable in partially leptin-deficient patients with partial lipodystrophy (PLD).

OBJECTIVE

Compare 3 leptin assays (Study I); identify diagnostic performance of leptin assays to detect responders to metreleptin for each assay (Study II).

DESIGN

Study I: cross-sectional analysis of average bias between leptin assays. Study II: retrospective analysis of diagnostic accuracy of potential leptin cut points to detect clinical responders to metreleptin.

SETTING

National Institutes of Health; University of Michigan.

PARTICIPANTS AND INTERVENTIONS

Study I: Metreleptin-naïve patients with lipodystrophy (GLD, n = 33, PLD, n = 67) and healthy volunteers (n = 239). Study II: GLD (n = 66) and PLD (n = 84) patients treated with metreleptin for 12 months.

OUTCOME MEASURES

Leptin concentrations by Millipore radioimmunoassay (RIA), Millipore enzyme-linked immunosorbent assay (MELISA), and R&D Systems enzyme-linked immunosorbent assay (RDELISA). Response to metreleptin therapy was defined as either reduction ≥1.0% in A1c or ≥30% in serum triglycerides.

RESULTS

RDELISA measured 3.0 ± 9.5 ng/mL higher than RIA; MELISA measured 11.0 ± 17.8 and 14.0 ±19.2 less than RIA and RDELISA, respectively. Leptin by RIA, MELISA, and RDELISA modestly predicted metreleptin response in GLD + PLD [receiver operating characteristic (ROC) area under the curve (AUC) 0.74, 0.69, and 0.71, respectively; P < 0.01 for all] with lower predictive power in PLD (ROC AUC 0.63, 0.61 and 0.65, respectively; P > 0.05 for all). The only reproducible cut point identified on sensitivity analyses was RIA leptin 7.2 ng/mL (sensitivity 56%; specificity 78%).

CONCLUSIONS

Three common leptin assays are not interchangeable, and a reliable cut point to select responders to metreleptin was not identified.

Cardiac phenotype in familial partial lipodystrophy

OBJECTIVES

LMNA variants have been previously associated with cardiac abnormalities independent of lipodystrophy. We aimed to assess cardiac impact of familial partial lipodystrophy (FPLD) to understand the role of laminopathy in cardiac manifestations.

STUDY DESIGN

Retrospective cohort study.

METHODS

Clinical data from 122 patients (age range: 13-77, 101 females) with FPLD were analysed. Mature human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a patient with an LMNA variant were studied as proof-of-concept for future studies.

RESULTS

Subjects with LMNA variants had a higher prevalence of overall cardiac events than others. The likelihood of having an arrhythmia was significantly higher in patients with LMNA variants (OR: 3.77, 95% CI: 1.45-9.83). These patients were at higher risk for atrial fibrillation or flutter (OR: 5.78, 95% CI: 1.04-32.16). The time to the first arrhythmia was significantly shorter in the LMNA group, with a higher HR of 3.52 (95% CI: 1.34-9.27). Non-codon 482 LMNA variants were more likely to be associated with cardiac events (vs. 482 LMNA: OR: 4.74, 95% CI: 1.41-15.98 for arrhythmia; OR: 17.67, 95% CI: 2.45-127.68 for atrial fibrillation or flutter; OR: 5.71, 95% CI: 1.37-23.76 for conduction disease). LMNA mutant hiPSC-CMs showed a higher frequency of spontaneous activity and shorter action potential duration. Functional syncytia of hiPSC-CMs displayed several rhythm alterations such as early afterdepolarizations, spontaneous quiescence and spontaneous tachyarrhythmia, and significantly slower recovery in chronotropic changes induced by isoproterenol exposure.

CONCLUSIONS

Our results highlight the need for vigilant cardiac monitoring in FPLD, especially in patients with LMNA variants who have an increased risk of developing cardiac arrhythmias. In addition, hiPSC-CMs can be studied to understand the basic mechanisms for the arrhythmias in patients with lipodystrophy to understand the impact of specific mutations.

The complicated clinical course in a case of atypical lipodystrophy after development of neutralizing antibody to metreleptin: treatment with setmelanotide

SUMMARY

A patient with atypical partial lipodystrophy who had a transient initial response to metreleptin experienced acute worsening of her metabolic state when neutralizing antibodies against metreleptin appeared. Because her metabolic status continued to deteriorate, a therapeutic trial with melanocortin-4 receptor agonist setmelanotide, that is believed to function downstream from leptin receptor in the leptin signaling system, was undertaken in an effort to improve her metabolic status for the first time in a patient with lipodystrophy. To achieve this, a compassionate use (investigational new drug application; IND) was initiated (NCT03262610). Glucose control, body fat by dual-energy X-ray absorptiometry and MRI, and liver fat by proton density fat fraction were monitored. Daily hunger scores were assessed by patient filled questionnaires. Although there was a slight decrease in hunger scales and visceral fat, stimulating melanocortin-4 receptor by setmelanotide did not result in any other metabolic benefit such as improvement of hypertriglyceridemia or diabetes control as desired. Targeting melanocortin-4 receptor to regulate energy metabolism in this setting was not sufficient to obtain a significant metabolic benefit. However, complex features of our case make it difficult to generalize these observations to all cases of lipodystrophy. It is still possible that melanocortin-4 receptor agonistic action may offer some therapeutic benefits in leptin-deficient patients.

LEARNING POINTS

A patient with atypical lipodystrophy with an initial benefit with metreleptin therapy developed neutralizing antibodies to metreleptin (Nab-leptin), which led to substantial worsening in metabolic control. The neutralizing activity in her serum persisted for longer than 3 years. Whether the worsening in her metabolic state was truly caused by the development of Nab-leptin cannot be fully ascertained, but there was a temporal relationship. The experience noted in our patient at least raises the possibility for concern for substantial metabolic worsening upon emergence and persistence of Nab-leptin. Further studies of cases where Nab-leptin is detected and better assay systems to detect and characterize Nab-leptin are needed. The use of setmelanotide, a selective MC4R agonist targeting specific neurons downstream from the leptin receptor activation, was not effective in restoring metabolic control in this complex patient with presumed diminished leptin action due to Nab-leptin. Although stimulating the MC4R pathway was not sufficient to obtain a significant metabolic benefit in lowering triglycerides and helping with her insulin resistance as was noted with metreleptin earlier, there was a mild reduction in reported food intake and appetite. Complex features of our case make it difficult to generalize our observation to all leptin-deficient patients. It is possible that some leptin-deficient patients (especially those who need primarily control of food intake) may still theoretically benefit from MC4R agonistic action, and further studies in carefully selected patients may help to tease out the differential pathways of metabolic regulation by the complex network of leptin signaling system.

Diagnosis of acquired generalized lipodystrophy in a single patient with T-cell lymphoma and no exposure to Metreleptin

Background

Metreleptin, a recombinant methionyl -human -leptin, was approved to treat patients with generalized lipodystrophy (GL) in February 2014. However, leptin therapy has been associated with the development of lymphoma. We present a unique case of a patient with prior history of T cell lymphoma in remission, who was diagnosed with Acquired Generalized Lipodystrophy (AGL) during the following year after a clinical remission of her lymphoma without receiving leptin therapy.

Case presentation

A 33-year-old woman with a diagnosis of stage IV subcutaneous panniculitis like T-cell lymphoma in 2011, underwent chemotherapy. Shortly after completion therapy, she had a relapse and required more chemotherapy with complete response, followed by allogenic stem cell transplant on June 28, 2012. Since that time, she has been on observation with no evidence of disease recurrence. Subsequent to the treatment, she was found to have high triglycerides, loss of fat tissue from her entire body and diagnosis of diabetes. Constellation of these findings led to the diagnosis of AGL in 2013. Her leptin level was low at 3.4 ng/mL (182 pmol/mL). She is currently not receiving any treatment with Metreleptin for her AGL.

Conclusions

Causal association between exogenous leptin therapy and T-cell lymphoma still remains unclear. We hereby present a case of a young woman who was diagnosed with AGL after going into remission from T-cell lymphoma and who has never been treated with Metreleptin. Steroid therapy and chemotherapy might have masked the diagnosis of AGL in this patient. We believe that patients can develop these 2 conditions independent of each other.

"Fat Shadows" From DXA for the Qualitative Assessment of Lipodystrophy: When a Picture Is Worth a Thousand Numbers

OBJECTIVE

Lipodystrophy syndromes are a heterogeneous group of disorders associated with selective absence of fat. Currently, the diagnosis is established only clinically.

RESEARCH DESIGN AND METHODS

We developed a new method from DXA scans called a "fat shadow," which is a color-coded representation highlighting only the fat tissue. We conducted a blinded retrospective validation study to assess its usefulness for the diagnosis of lipodystrophy syndromes.

RESULTS

We evaluated the fat shadows from 16 patients (11 female and 5 male) with generalized lipodystrophy (GL), 57 (50 female and 7 male) with familial partial lipodystrophy (FPLD), 2 (1 female and 1 male) with acquired partial lipodystrophy, and 126 (90 female and 36 male) control subjects. FPLD was differentiated from control subjects with 85% sensitivity and 96% specificity (95% CIs 72-93 and 91-99, respectively). GL was differentiated from nonobese control subjects with 100% sensitivity and specificity (95% CIs 79-100 and 92-100, respectively).

CONCLUSIONS

Fat shadows provided sufficient qualitative information to infer clinical phenotype and differentiate these patients from appropriate control subjects. We propose that this method could be used to support the diagnosis.

Spectrum of disease associated with partial lipodystrophy: lessons from a trial cohort

CONTEXT

Partial lipodystrophy (PL) is associated with metabolic co-morbidities but may go undiagnosed as the disease spectrum is not fully described.

OBJECTIVE

The objective of the study was to define disease spectrum in PL using genetic, clinical (historical, morphometric) and laboratory characteristics.

DESIGN

Cross-sectional evaluation.

PARTICIPANTS

Twenty-three patients (22 with familial, one acquired, 78·3% female, aged 12-64 years) with PL and non-alcoholic fatty liver disease (NAFLD).

MEASUREMENTS

Genetic, clinical and laboratory characteristics, body composition indices, liver fat content by magnetic resonance imaging (MRI), histopathological and immunofluorescence examinations of liver biopsies.

RESULTS

Seven patients displayed heterozygous pathogenic variants in LMNA. Two related patients had a heterozygous, likely pathogenic novel variant of POLD1 (NM002691·3: c.3199 G>A; p.E1067K). Most patients had high ratios (>1·5) of percentage fat trunk to percentage fat legs (FMR) when compared to reference normals. Liver fat quantified using MR Dixon method was high (11·3 ± 6·3%) and correlated positively with haemoglobin A1c and triglycerides while leg fat by dual-energy X-ray absorptiometry (DEXA) correlated negatively with triglycerides. In addition to known metabolic comorbidities; chronic pain (78·3%), hypertension (56·5%) and mood disorders (52·2%) were highly prevalent. Mean NAFLD Activity Score (NAS) was 5 ± 1 and 78·3% had fibrosis. LMNA-immunofluorescence staining from select patients (including one with the novel POLD1 variant) showed a high degree of nuclear atypia and disorganization.

CONCLUSIONS

Partial lipodystrophy is a complex multi-system disorder. Metabolic parameters correlate negatively with extremity fat and positively with liver fat. DEXA-based FMR may prove useful as a diagnostic tool. Nuclear disorganization and atypia may be a common biomarker even in the absence of pathogenic variants in LMNA.

Efficacy and Safety of Metreleptin in Patients with Partial Lipodystrophy: Lessons from an Expanded Access Program

OBJECTIVE

Patients with lipodystrophy have severe metabolic abnormalities (insulin resistance, diabetes, and hypertriglyceridemia) that may increase morbidity and mortality. Metreleptin is approved by the United States Food and Drug Administration for treatment of generalized forms of lipodystrophy. We aimed to determine the efficacy and safety of metreleptin among patients with partial lipodystrophy using an expanded-access model.

METHODS

Study FHA101 (ClinicalTrials.gov identifier: NCT00677313) was an open-label, expanded-access, long-term clinical effectiveness and safety study in 23 patients with partial lipodystrophy and diabetes and/or hypertriglyceridemia with no prespecified leptin level. Metreleptin was administered subcutaneously at 0.02 mg/kg twice daily (BID) at Week 1, followed by 0.04 mg/kg BID at Week 2. Dose adjustments thereafter were based on patient response (maximum dose of 0.08 mg/kg BID). One-year changes in glycated hemoglobin (HbA1c), fasting plasma glucose, triglycerides, alanine and aspartate aminotransferases, and treatment-emergent adverse events (TEAEs) were evaluated.

RESULTS

HbA1c, fasting plasma glucose, and triglycerides were numerically decreased throughout 1 year, with mean (standard error) changes from baseline of -0.88 (0.62)%, -42.0 (22.4) mg/dL, and -119.8 (84.1) mg/dL, respectively, which were greater among patients with higher baseline abnormalities. Liver enzymes did not worsen, and the most frequently observed TEAEs (≥ 10% incidence) were mild to moderate and included nausea (39.1%), hypoglycemia (26.1%), and urinary tract infections (26.1%)-all reported previously. There were no reports of clinically significant immune-related adverse events or new safety signals.

CONCLUSIONS

Our clinical observations document the large heterogeneity and disease burden of partial lipodystrophy syndromes and suggest that metreleptin treatment benefits may extend to patients with partial lipodystrophy. Additional studies are needed to confirm these preliminary findings.

Intraspecific polymorphism to interspecific divergence: genetics of pigmentation in Drosophila

Genetic changes contributing to phenotypic differences within or between species have been identified for a handful of traits, but the relationship between alleles underlying intraspecific polymorphism and interspecific divergence is largely unknown. We found that noncoding changes in the tan gene, as well as changes linked to the ebony gene, contribute to pigmentation divergence between closely related Drosophila species. Moreover, we found that alleles linked to tan and ebony fixed in one Drosophila species also contribute to variation within another species, and that multiple genotypes underlie similar phenotypes even within the same population. These alleles appear to predate speciation, which suggests that standing genetic variation present in the common ancestor gave rise to both intraspecific polymorphism and interspecific divergence.

Lamprey Dlx genes and early vertebrate evolution

Gnathostome vertebrates have multiple members of the Dlx family of transcription factors that are expressed during the development of several tissues considered to be vertebrate synapomorphies, including the forebrain, cranial neural crest, placodes, and pharyngeal arches. The Dlx gene family thus presents an ideal system in which to examine the relationship between gene duplication and morphological innovation during vertebrate evolution. Toward this end, we have cloned Dlx genes from the lamprey Petromyzon marinus, an agnathan vertebrate that occupies a critical phylogenetic position between cephalochordates and gnathostomes. We have identified four Dlx genes in P. marinus, whose orthology with gnathostome Dlx genes provides a model for how this gene family evolved in the vertebrate lineage. Differential expression of these lamprey Dlx genes in the forebrain, cranial neural crest, pharyngeal arches, and sensory placodes of lamprey embryos provides insight into the developmental evolution of these structures as well as a model of regulatory evolution after Dlx gene duplication events.

Amphioxus goosecoid and the evolution of the head organizer and prechordal plate

The organizer is a central feature of vertebrate embryogenesis and is functionally subdivided into the head organizer that gives rise primarily to the prechordal plate and induces forebrain structures, and the trunk/tail organizer that gives rise primarily to the notochord and induces more posterior structures. Goosecoid(gsc) encodes a homeodomain-containing transcription factor that is expressed in the vertebrate head organizer and prechordal plate, and can induce a secondary axis when expressed ectopically. To investigate the evolution of the vertebrate head organizer and prechordal plate, we have cloned and characterized a gsc homolog from the cephalochordate amphioxus. Amphioxus, it is important to note, lacks a prechordal plate in that the notochord extends to the extreme anterior end of the animal, and lacks elaborate differentiation of its forebrain. Gsc expression in amphioxus is initially localized during gastrulation to the mesendodermal layer of the dorsal lip of the blastopore. However, gsc expression in amphioxus is not maintained in anterior axial mesoderm, as is the case with the vertebrate prechordal plate. Rather, gsc is expressed in the dorsal axial mesoderm of the blastopore lip throughout gastrulation, appearing transiently in the presumptive notochord that underlies all regions of the amphioxus brain. The similarities in gsc expression in amphioxus and vertebrates suggest that a primitive version of the head organizer evolved prior to the origin of the vertebrates. The differences in gsc expression can be interpreted either as the loss of the prechordal plate domain in the cephalochordate lineage, or the gain of a distinct gsc-expressing prechordal plate that plays a role in forebrain induction in the vertebrate lineage.