Inebilizumab reduces neuromyelitis optica spectrum disorder risk independent of FCGR3A polymorphism

Inebilizumab, a humanized, glycoengineered, IgG1 monoclonal antibody that depletes CD19+ B-cells, is approved to treat aquaporin 4 (AQP4) IgG-seropositive neuromyelitis optica spectrum disorder (NMOSD). Inebilizumab is afucosylated and engineered for enhanced affinity to Fc receptor III-A (FCGR3A) receptors on natural killer cells to maximize antibody-dependent cellular cytotoxicity. Previously, the F allele polymorphism at amino acid 158 of the FCGR3A gene (F158) was shown to decrease IgG-binding affinity and reduce rituximab (anti-CD20) efficacy for NMOSD attack prevention. In contrast, our current findings from inebilizumab-treated NMOSD patients indicate similar clinical outcomes between those with F158 and V158 allele genotypes.

Efficacy and Safety of Inebilizumab in IgG4-Related Disease: Protocol for a Randomized Controlled Trial

INTRODUCTION

Immunoglobulin G4-related disease (IgG4-RD) is a debilitating multiorgan disease characterized by recurring flares leading to organ dysfunction, decreased quality of life, and mortality. Glucocorticoids, the standard of care for IgG4-RD, are associated with substantial treatment-related toxicity. Inebilizumab, an antibody directed against CD19, mediates the rapid and durable depletion of CD19+ B cells thought to be involved in IgG4-RD pathogenesis. We describe the first international, prospective, double-blind, placebo-controlled trial to evaluate the safety and efficacy of B-cell depletion for flare prevention in IgG4-RD (MITIGATE).

METHODS

The study was designed by an international panel of physicians with expertise in IgG4-RD. Critical trial design decisions included the selection of participants, definition of clinically meaningful primary and secondary endpoints, accommodation of standard of care, and development of flare diagnostic criteria. The study is approved for conduct in 22 countries.

PLANNED OUTCOMES

The primary efficacy endpoint is time from randomization to the occurrence of the first centrally adjudicated and investigator-treated disease flare during the 1-year randomized controlled period. A set of novel, organ-specific flare diagnostic criteria were developed specifically for this trial, incorporating symptoms and signs, laboratory findings, imaging study results, and pathology data. MITIGATE aims to accrue 39 flares for the primary endpoint, which provides sufficient power to detect a relative risk reduction of 65% in the inebilizumab group. It is anticipated that enrollment of 160 participants will achieve this goal. Additional endpoints include safety, annualized flare rate, flare-free complete remission, quality-of-life measures, and cumulative glucocorticoid use. MITIGATE represents the first randomized, double-blind, placebo-controlled trial of any treatment strategy conducted in IgG4-RD. Data from this study will provide insights into the natural history and pathophysiology of IgG4-RD and the efficacy and safety of B-cell depletion as a therapeutic avenue.

TRIAL REGISTRATION

NCT04540497.

Serum neurofilament light chain levels at attack predict post-attack disability worsening and are mitigated by inebilizumab: analysis of four potential biomarkers in neuromyelitis optica spectrum disorder

OBJECTIVE

To investigate relationships between serum neurofilament light chain (sNfL), ubiquitin C-terminal hydrolase L1 (sUCHL1), tau (sTau) and glial fibrillary acidic protein (sGFAP) levels and disease activity/disability in neuromyelitis optica spectrum disorder (NMOSD), and the effects of inebilizumab on these biomarkers in N-MOmentum.

METHODS

N-MOmentum randomised participants to receive inebilizumab or placebo with a randomised controlled period (RCP) of 28 weeks and an open-label follow-up period of ≥2 years. The sNfL, sUCHL1, sTau and sGFAP were measured using single-molecule arrays in 1260 scheduled and attack-related samples from N-MOmentum participants (immunoglobulin G (IgG) autoantibodies to aquaporin-4-positive, myelin oligodendrocyte glycoprotein-IgG-positive or double autoantibody-negative) and two control groups (healthy donors and patients with relapsing-remitting multiple sclerosis).

RESULTS

The concentration of all four biomarkers increased during NMOSD attacks. At attack, sNfL had the strongest correlation with disability worsening during attacks (Spearman R2=0.40; p=0.01) and prediction of disability worsening after attacks (sNfL cut-off 32 pg/mL; area under the curve 0.71 (95% CI 0.51 to 0.89); p=0.02), but only sGFAP predicted upcoming attacks. At RCP end, fewer inebilizumab-treated than placebo-treated participants had sNfL>16 pg/mL (22% vs 45%; OR 0.36 (95% CI 0.17 to 0.76); p=0.004).

CONCLUSIONS

Compared with sGFAP, sTau and sUCHL1, sNfL at attack was the strongest predictor of disability worsening at attack and follow-up, suggesting a role for identifying participants with NMOSD at risk of limited post-relapse recovery. Treatment with inebilizumab was associated with lower levels of sGFAP and sNfL than placebo.

TRIAL REGISTRATION NUMBER

NCT02200770.

Attack adjudication in neuromyelitis optica spectrum disorder: Substantiation of criteria by magnetic resonance imaging and biomarkers in N-MOmentum

BACKGROUND

The N-MOmentum trial investigated safety and efficacy of inebilizumab in participants with neuromyelitis optica spectrum disorder (NMOSD).

OBJECTIVE

Evaluate the attack identification process and adjudication committee (AC) performance in N-MOmentum.

METHODS

Adults (n = 230) with NMOSD and Expanded Disability Status Scale score ⩽8 were randomized (3:1) to inebilizumab 300 mg or placebo. The randomized controlled period was 28 weeks or until adjudicated attack. Attacks were adjudicated according to 18 predefined criteria. Magnetic resonance imaging (MRI) and biomarker (serum glial fibrillary acidic protein [sGFAP]) analyses were performed.

RESULTS

A total of 64 participant-reported neurological events occurred; 51 (80%) were investigator-determined to be attacks. The AC confirmed 43 of the investigator-determined attacks (84%). There was high inter- and intra-AC-member agreement. In 25/64 events (39%) and 14/43 AC-adjudicated attacks (33%), MRI was reviewed during adjudication. Retrospective analysis revealed new domain-specific T1 and T2 MRI lesions in 90% of adjudicated attacks. Increased mean sGFAP concentrations (>2-fold change) from baseline were observed in 56% of adjudicated attacks versus 14% of investigator-determined attacks rejected by the AC and 31% of participant-reported events determined not to be attacks.

CONCLUSION

AC adjudication of NMOSD attacks according to predefined criteria appears robust. MRI lesion correlates and sGFAP elevations were found in most adjudicated attacks.

Pharmacodynamic modeling and exposure-response assessment of inebilizumab in subjects with neuromyelitis optica spectrum disorders

Aims

Neuromyelitis optica spectrum disorders (NMOSD) is an autoantibody‐mediated, B cell‐driven disease. Inebilizumab is a humanized, affinity‐optimized, afucosylated IgG1 κ monoclonal antibody that binds to the B‐cell specific surface antigen CD19, resulting in rapid, profound and sustained depletion of circulating peripheral B cells in NMOSD subjects (pivotal study). The objective of this study was to conduct population modelling of B‐cell response following inebilizumab treatment in adult subjects with NMOSD, and to assess the impact of drug exposure to outcome.

Methods

A haematopoietic transit model was developed to describe the joint effects of reducing influx from pro‐B cells and accelerating CD20⁺ B‐cell depletion in the blood by inebilizumab. Furthermore, the relationships between inebilizumab pharmacokinetic (PK) exposure and the primary efficacy endpoint and key secondary efficacy endpoints were evaluated.

Results

At the 300‐mg dose, there was no apparent relationship between efficacy (reduction in disease attack risk, risk of worsening from baseline in Expanded Disability Status Scale, cumulative total active MRI lesions, and the number of NMOSD‐related in‐patient hospitalizations) and PK exposure. Subjects with low, medium and high PK exposure had a similar hazard ratio of NMOSD attack vs. placebo group.

Conclusion

The pharmacodynamic modelling confirmed effective depletion of B cells is achieved with a 300 mg intravenous dose of inebilizumab administered on Day 1 and Day 15 and every 6 months thereafter. The PK variability between patients had no apparent effect on clinical efficacy.

Inebilizumab for treatment of neuromyelitis optica spectrum disorder in patients with prior rituximab use from the N-MOmentum Study

BACKGROUND

The B-cell-depleting agent rituximab (anti-CD20) was historically used to prevent attacks in neuromyelitis optica spectrum disorder (NMOSD). Inebilizumab, which targets and depletes CD19-expressing B cells, plasmablasts, and some plasma cells, received approval from the US Food and Drug Administration for treatment of NMOSD based on results from the randomized, placebo-controlled, phase 2/3 N-MOmentum trial. Because of their closely related mechanisms of action, consideration as to whether inebilizumab may be a suitable treatment option for patients with prior rituximab experience is important. This post hoc analysis of data from N-MOmentum assessed inebilizumab efficacy and tolerability in participants previously treated with rituximab.

METHODS

Adjudicated attacks, secondary efficacy outcomes, and treatment-emergent adverse events were assessed by prior rituximab use during a 6-month randomized control period and open-label period.

RESULTS

Seventeen participants in N-MOmentum had prior rituximab use, of whom 13 were randomly assigned to the inebilizumab treatment group. Seven of these participants had breakthrough attacks prior to enrollment (annualized attack rate, 0.78 attacks/person-year) despite rituximab use. While they were receiving inebilizumab in the randomized control period, 1 of 13 participants with prior rituximab use had an attack (hazard ratio vs all placebo, 0.16; 95% confidence interval: 0.02 1.20; p = 0.07). Two additional participants with prior rituximab use experienced attacks on inebilizumab during the open-label period, with an overall annualized attack rate of 0.08 (95% confidence interval: 0.02 0.34) attacks/person-year. This annualized attack rate was similar to that of participants without prior rituximab use (0.10 [95% confidence interval: 0.07 0.15]). None of the 7 participants who experienced attacks while taking rituximab experienced an attack while receiving inebilizumab. Two (12%) participants with prior rituximab use experienced serious treatment-emergent adverse events related to inebilizumab, with serious or grade ≥3 infections occurring in 3 (18%) participants each. No deaths or opportunistic infections were reported in this cohort.

CONCLUSIONS

These findings support the efficacy of inebilizumab in participants with NMOSD who had previously been treated with rituximab. Infections occurred in nearly all study participants with prior rituximab exposure, highlighting a need for clinical vigilance in such individuals. Further studies are necessary to determine potential safety concerns of inebilizumab, including risk of infection, in rituximab-experienced patients. ClinicalTrials.gov identifier: NCT02200770.

Population Pharmacokinetic Modeling of Inebilizumab in Subjects with Neuromyelitis Optica Spectrum Disorders, Systemic Sclerosis, or Relapsing Multiple Sclerosis

Background and Objective

Inebilizumab is a humanized, affinity-optimized, afucosylated immunoglobulin (Ig)-G1κ monoclonal antibody that binds to CD19, resulting in effective depletion of peripheral B cells. It is being developed to treat various autoimmune diseases, including neuromyelitis optica spectrum disorders (NMOSD), systemic sclerosis (SSc), and relapsing multiple sclerosis (MS).

Methods

Pharmacokinetic data from a pivotal study in adult subjects with NMOSD and two early-stage studies in subjects with SSc or relapsing MS were pooled and simultaneously analyzed using a population approach.

Results

Upon intravenous administration, the pharmacokinetics of inebilizumab were adequately described by a two-compartment model with parallel first-order and time-dependent nonlinear elimination pathways. An asymptotic nonlinear elimination suggests that inebilizumab undergoes receptor (CD19)-mediated clearance. The estimated systemic clearance (CL) of the first-order elimination pathway (0.188 L/day) and the volume of distribution (V_d) (5.52 L) were typical for therapeutic immunoglobulins. The elimination half-life was approximately 18 days. The maximum velocity (V_max) of the nonlinear elimination pathway decreased with time, presumably due to the depletion of B cells upon inebilizumab administration. As for other therapeutic monoclonal antibodies, the CL and V_d of inebilizumab increased with body weight.

Conclusions

The presence of antidrug antibodies, status of hepatic or renal function, and use of small-molecule drugs commonly used by subjects with NMOSD had no clinically relevant impact on the pharmacokinetics of inebilizumab. The nonlinear elimination pathway at the 300 mg therapeutic dose level is not considered clinically relevant.

Long-term efficacy and safety of inebilizumab in neuromyelitis optica spectrum disorder: Analysis of aquaporin-4-immunoglobulin G-seropositive participants taking inebilizumab for ⩾4 years in the N-MOmentum trial

Background:

Efficacy and safety of inebilizumab for treatment of neuromyelitis optica spectrum disorder in adults seropositive for aquaporin-4 (AQP4)–immunoglobulin (Ig) G were demonstrated in the 28-week randomized controlled period of the N-MOmentum study.

Objective:

To assess efficacy and safety of long-term inebilizumab treatment.

Methods:

Post hoc analysis was performed in 75 AQP4–IgG–seropositive participants receiving inebilizumab for ⩾4 years in the randomized controlled period and open-label extension of the N-MOmentum study.

Results:

Eighteen attacks occurred in 13 participants during inebilizumab treatment (annualized attack rate, 0.052 attacks/person-year). Twelve attacks occurred during the first year of treatment, and two each occurred in years 2–4. Disability scores remained stable throughout ⩾4 years of treatment. Inebilizumab was well tolerated, with two (2.7%) serious treatment-emergent adverse events related to inebilizumab and no deaths. Immunoglobulin G levels decreased over time; however, correlation between severe infections and low IgG levels could not be determined because of their small numbers.

Conclusion:

These results from the N-MOmentum study continue to support use of inebilizumab for treatment of neuromyelitis optica spectrum disorder. Furthermore, the findings suggest that efficacy of inebilizumab may be enhanced after the first year of treatment, warranting additional long-term investigation.

Disability Outcomes in the N-MOmentum Trial of Inebilizumab in Neuromyelitis Optica Spectrum Disorder

Objective

To assess treatment effects on Expanded Disability Status Scale (EDSS) score worsening and modified Rankin Scale (mRS) scores in the N-MOmentum trial of inebilizumab, a humanized anti-CD19 monoclonal antibody, in participants with neuromyelitis optica spectrum disorder (NMOSD).

Methods

Adults (N = 230) with aquaporin-4 immunoglobulin G-seropositive NMOSD or -seronegative neuromyelitis optica and an EDSS score ≤8 were randomized (3:1) to receive inebilizumab 300 mg or placebo on days 1 and 15. The randomized controlled period (RCP) was 28 weeks or until adjudicated attack, with an option to enter the inebilizumab open-label period. Three-month EDSS-confirmed disability progression (CDP) was assessed using a Cox proportional hazard model. The effect of baseline subgroups on disability was assessed by interaction tests. mRS scores from the RCP were analyzed by the Wilcoxon-Mann-Whitney odds approach.

Results

Compared with placebo, inebilizumab reduced the risk of 3-month CDP (hazard ratio [HR]: 0.375; 95% CI: 0.148–0.952; p = 0.0390). Baseline disability, prestudy attack frequency, and disease duration did not affect the treatment effect observed with inebilizumab (HRs: 0.213–0.503; interaction tests: all p > 0.05, indicating no effect of baseline covariates on outcome). Mean EDSS scores improved with longer-term treatment. Inebilizumab-treated participants were more likely to have a favorable mRS outcome at the end of the RCP (OR: 1.663; 95% CI: 1.195–2.385; p = 0.0023).

Conclusions

Disability outcomes were more favorable with inebilizumab vs placebo in participants with NMOSD.

Classification of Evidence

This study provides Class II evidence that for patients with NMOSD, inebilizumab reduces the risk of worsening disability. N-MOmentum is registered at ClinicalTrials.gov: NCT02200770.

Sensitivity analysis of the primary endpoint from the N-MOmentum study of inebilizumab in NMOSD

Background:

In the N-MOmentum trial, the risk of an adjudicated neuromyelitis optica spectrum disorder (NMOSD) attack was significantly reduced with inebilizumab compared with placebo.

Objective:

To demonstrate the robustness of this finding, using pre-specified sensitivity and subgroup analyses.

Methods:

N-MOmentum is a prospective, randomized, placebo-controlled, double-masked trial of inebilizumab, an anti-CD19 monoclonal B-cell-depleting antibody, in patients with NMOSD. Pre-planned and post hoc analyses were performed to evaluate the primary endpoint across a range of attack definitions and demographic groups, as well as key secondary endpoints.

Results:

In the N-MOmentum trial (ClinicalTrials.gov: NCT02200770), 174 participants received inebilizumab and 56 received placebo. Attack risk for inebilizumab versus placebo was consistently and significantly reduced, regardless of attack definition, type of attack, baseline disability, ethnicity, treatment history, or disease course (all with hazard ratios < 0.4 favoring inebilizumab, p < 0.05). Analyses of secondary endpoints showed similar trends.

Conclusion:

N-MOmentum demonstrated that inebilizumab provides a robust reduction in the risk of NMOSD attacks regardless of attack evaluation method, attack type, patient demographics, or previous therapy.

The N-MOmentum study is registered at ClinicalTrials.gov: NCT2200770.

Inebilizumab for the treatment of neuromyelitis optica spectrum disorder (N-MOmentum): a double-blind, randomised placebo-controlled phase 2/3 trial

BACKGROUND

No approved therapies exist for neuromyelitis optica spectrum disorder (NMOSD), a rare, relapsing, autoimmune, inflammatory disease of the CNS that causes blindness and paralysis. We aimed to assess the efficacy and safety of inebilizumab, an anti-CD19, B cell-depleting antibody, in reducing the risk of attacks and disability in NMOSD.

METHODS

We did a multicentre, double-blind, randomised placebo-controlled phase 2/3 study at 99 outpatient specialty clinics or hospitals in 25 countries. Eligible participants were adults (≥18 years old) with a diagnosis of NMOSD, an Expanded Disability Status Scale score of 8·0 or less, and a history of at least one attack requiring rescue therapy in the year before screening or at least two attacks requiring rescue therapy in the 2 years before screening. Participants were randomly allocated (3:1) to 300 mg intravenous inebilizumab or placebo with a central interactive voice response system or interactive web response system and permuted block randomisation. Inebilizumab or placebo was administered on days 1 and 15. Participants, investigators, and all clinical staff were masked to the treatments, and inebilizumab and placebo were indistinguishable in appearance. The primary endpoint was time to onset of an NMOSD attack, as determined by the adjudication committee. Efficacy endpoints were assessed in all randomly allocated patients who received at least one dose of study intervention, and safety endpoints were assessed in the as-treated population. The study is registered with ClinicalTrials.gov, number NCT02200770.

FINDINGS

Between Jan 6, 2015, and Sept 24, 2018, 230 participants were randomly assigned to treatment and dosed, with 174 participants receiving inebilizumab and 56 receiving placebo. The randomised controlled period was stopped before complete enrolment, as recommended by the independent data-monitoring committee, because of a clear demonstration of efficacy. 21 (12%) of 174 participants receiving inebilizumab had an attack versus 22 (39%) of 56 participants receiving placebo (hazard ratio 0·272 [95% CI 0·150-0·496]; p<0·0001). Adverse events occurred in 125 (72%) of 174 participants receiving inebilizumab and 41 (73%) of 56 participants receiving placebo. Serious adverse events occurred in eight (5%) of 174 participants receiving inebilizumab and five (9%) of 56 participants receiving placebo.

INTERPRETATION

Compared with placebo, inebilizumab reduced the risk of an NMOSD attack. Inebilizumab has potential application as an evidence-based treatment for patients with NMOSD.

FUNDING

MedImmune and Viela Bio.

Safety and tolerability of an anti-CD19 monoclonal antibody, MEDI-551, in subjects with systemic sclerosis: a phase I, randomized, placebo-controlled, escalating single-dose study

Background

Systemic sclerosis (SSc) is a clinically heterogeneous, life-threatening disease characterized by fibrosis, microvasculopathy, and autoimmunity. Extensive nonclinical and clinical data implicate B cells in the pathogenesis of SSc. MEDI-551 is an investigational humanized monoclonal antibody that targets the B cell surface antigen CD19 and mediates antibody-dependent, cell-mediated cytotoxicity of B cells. This clinical study evaluated the safety and tolerability, pharmacokinetics, and pharmacodynamics of MEDI-551 in subjects with SSc.

Methods

This phase I multicenter, randomized, double-blind, placebo-controlled, single escalating dose study enrolled adult subjects with either limited or diffuse cutaneous SSc. A single intravenous dose of MEDI-551 was administered, and safety and tolerability were evaluated. MEDI-551 pharmacokinetics (PK), pharmacodynamics, and immunogenicity were also assessed. Safety assessments included the incidence of adverse events and changes in clinical and laboratory results. MEDI-551 serum concentrations, effects on circulating and tissue B cells and plasma cells (PCs), and antidrug antibodies were analyzed. Modified Rodnan skin score (MRSS) and pulmonary function tests were used to explore the clinical effect of MEDI-551.

Results

The study enrolled 28 subjects with SSc (mean age, 47.3 years; 67.9 % female). Twenty-four received a single dose of MEDI-551 (0.1–10.0 mg/kg) and four received placebo. Treatment-emergent adverse events (TEAEs) occurred in 95.8 % of subjects in the MEDI-551 group and in 75.0 % of subjects in the placebo group; the majority of TEAEs were mild or moderate in severity. Two serious adverse events were considered possibly related to the study drug. One death, deemed not related to the study drug, occurred in a MEDI-551-treated subject. MEDI-551 exhibited linear PK in the dose range of 1.0 to 10.0 mg/kg, and more rapid clearance at lower doses. Dose-dependent depletion of circulating B cells and plasma cells was observed. MRSS assessments suggest a possible clinical effect of MEDI-551 on affected skin.

Conclusions

A single escalating dose of MEDI-551 was tolerable and safe in this subject population. B cell depletion was achieved and was dose dependent. A signal of clinical effect was observed. Based on these results, further investigation of MEDI-551 as a disease-modifying treatment for SSc is warranted.

Trial registration

www.clinicaltrials.gov identifier, NCT00946699; registered 23 July 2009.

Discovery of (2S)-1-[4-(2-{6-amino-8-[(6-bromo-1,3-benzodioxol-5-yl)sulfanyl]-9H-purin-9-yl}ethyl)piperidin-1-yl]-2-hydroxypropan-1-one (MPC-3100), a purine-based Hsp90 inhibitor

Modulation of Hsp90 (heat shock protein 90) function has been recognized as an attractive approach for cancer treatment, since many cancer cells depend on Hsp90 to maintain cellular homeostasis. This has spurred the search for small-molecule Hsp90 inhibitors. Here we describe our lead optimization studies centered on the purine-based Hsp90 inhibitor 28a containing a piperidine moiety at the purine N9 position. In this study, key SAR was established for the piperidine N-substituent and for the congeners of the 1,3-benzodioxole at C8. These efforts led to the identification of orally bioavailable 28g that exhibits good in vitro profiles and a characteristic molecular biomarker signature of Hsp90 inhibition both in vitro and in vivo. Favorable pharmacokinetic properties along with significant antitumor effects in multiple human cancer xenograft models led to the selection of 28g (MPC-3100) as a clinical candidate.

Abstract 2617: MPC-3100, a synthetic Hsp90 inhibitor, induces biomarker changes in vitro and in vivo

Introduction: MPC-3100 is a fully synthetic, orally bioavailable, Hsp90 inhibitor in clinical development. It is broadly active in xenograft models with anti-tumor activity ranging from tumor regression to tumor growth inhibition in many cancer types including colon, gastric, ovarian, prostate, breast, lung and myeloid leukemia. Here we evaluate the effect of MPC-3100 on stability of client proteins in cells and xenograft tumors. We also determine the effect on Hsp70 protein levels, a biomarker of Hsp90 inhibition, in peripheral blood mononuclear cells (PBMCs) from cancer patients receiving MPC-3100.

Methods: Her2, Akt, Cdk4, c-Raf and Hsp70 client protein levels were monitored in cell culture with protein immunoblots. Formalin-fixed, paraffin-embedded sections of xenograft tumors from mice dosed orally with MPC-3100 were analyzed by immunohistochemistry (IHC) to monitor changes in Her2, Akt and Hsp70 protein levels. To monitor changes in Hsp70 in cancer patients treated with MPC-3100, PBMCs were collected prior to drug administration, 8 and 24 hours post-dose on Day 1 and 24 hours post-dose on Days 7 and 21 of the first treatment cycle. Hsp70 protein levels were determined by ELISA.

Results: Exposure of HCT-116, NCI-N87 and DU-145 cells to MPC-3100 in vitro resulted in a time-dependent reduction in client protein levels with maximal reduction by 24 hours. The IC50 values for client protein reduction ranged from 0.1 μM to 0.5 μM, comparable to the cellular cytotoxicity values of MPC-3100 at 72 hours for the various cell lines. IHC revealed reduction in Her2 and Akt protein in N87 xenografts in mice given a single oral dose of 200 mg/kg MPC-3100 relative to tumors from animals dosed with vehicle. Healthy volunteer PBMCs exposed to 1 μM MPC-3100 for 24 hours ex vivo revealed a reduction in Akt, c-Raf and Cdk4 protein levels ranging from 50% to 90%. PBMCs from cancer patients receiving MPC-3100 showed an increase of 28 to 589 ng of Hsp70 protein per mg total protein over baseline by Day 8. The increase in Hsp70 expression was seen as early as 8 hours after the first dose and sustained through at least Day 22.

Conclusions: The changes in client proteins and biomarkers observed in cells and tumor xenografts exposed to MPC-3100 confirm that the cellular cytotoxic activity and anti-tumor activity in xenografts are a result of Hsp90 inhibition. The consistent increase in Hsp70 expression in PBMCs from cancer patients receiving MPC-3100 indicates that Hsp90 function is inhibited in patients at doses that have been well tolerated in the clinic.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2617. doi:10.1158/1538-7445.AM2011-2617

Marine natural product libraries for high-throughput screening and rapid drug discovery

There is a need for diverse molecular libraries for phenotype-selective and high-throughput screening. To make marine natural products (MNPs) more amenable to newer screening paradigms and shorten discovery time lines, we have created an MNP library characterized online using MS. To test the potential of the library, we screened a subset of the library in a phenotype-selective screen to identify compounds that inhibited the growth of BRCA2-deficient cells.

The beta-globin LCR is not necessary for an open chromatin structure or developmentally regulated transcription of the native mouse beta-globin locus

The murine beta-globin locus control region (LCR) was deleted from its native chromosomal location. The approximately 25 kb deletion eliminates all sequences and structures homologous to those defined as the human LCR. In differentiated ES cells and erythroleukemia cells containing the LCR-deleted chromosome, DNasel sensitivity of the beta-globin domain is established and maintained, developmental regulation of the locus is intact, and beta-like globin RNA levels are reduced 5%-25% of normal. Thus, in the native murine beta-globin locus, the LCR is necessary for normal levels of transcription, but other elements are sufficient to establish the open chromatin structure, transcription, and developmental specificity of the locus. These findings suggest a contributory rather than dominant function for the LCR in its native location.

The locus control region is necessary for gene expression in the human beta-globin locus but not the maintenance of an open chromatin structure in erythroid cells

Studies in many systems have led to the model that the human beta-globin locus control region (LCR) regulates the transcription, chromatin structure, and replication properties of the beta-globin locus. However the precise mechanisms of this regulation are unknown. We have developed strategies to use homologous recombination in a tissue culture system to examine how the LCR regulates the locus in its natural chromosomal environment. Our results show that when the functional components of the LCR, as defined by transfection and transgenic studies, are deleted from the endogenous beta-globin locus in an erythroid background, transcription of all beta-globin genes is abolished in every cell. However, formation of the remaining hypersensitive site(s) of the LCR and the presence of a DNase I-sensitive structure of the beta-globin locus are not affected by the deletion. In contrast, deletion of 5'HS5 of the LCR, which has been suggested to serve as an insulator, has only a minor effect on beta-globin transcription and does not influence the chromatin structure of the locus. These results show that the LCR as currently defined is not necessary to keep the locus in an "open" conformation in erythroid cells and that even in an erythroid environment an open locus is not sufficient to permit transcription of the beta-like globin genes.