Discovery of Sulanemadlin (ALRN-6924), the First Cell-Permeating, Stabilized α-Helical Peptide in Clinical Development

We report the discovery of sulanemadlin (ALRN-6924), the first cell-permeating, stabilized α-helical peptide to enter clinical trials. ALRN-6924 is a "stapled peptide" that mimics the N-terminal domain of the p53 tumor suppressor protein. It binds with high affinity to both MDM2 and MDMX (also known as MDM4), the endogenous inhibitors of p53, to activate p53 signaling in cells having a non-mutant, or wild-type TP53 genotype (TP53-WT). Iterative structure-activity optimization endowed ALRN-6924 with favorable cell permeability, solubility, and pharmacokinetic and safety profiles. Intracellular proteolysis of ALRN-6924 forms a long-acting active metabolite with potent MDM2 and MDMX binding affinity and slow dissociation kinetics. At high doses, ALRN-6924 exhibits on-mechanism anticancer activity in TP53-WT tumor models. At lower doses, ALRN-6924 transiently arrests the cell cycle in healthy tissues to protect them from chemotherapy without protecting the TP53-mutant cancer cells. These results support the continued clinical evaluation of ALRN-6924 as an anticancer and chemoprotection agent.

Pharmacologic Activation of p53 Triggers Viral Mimicry Response Thereby Abolishing Tumor Immune Evasion and Promoting Antitumor Immunity

The repression of repetitive elements is an important facet of p53's function as a guardian of the genome. Paradoxically, we found that p53 activated by MDM2 inhibitors induced the expression of endogenous retroviruses (ERV) via increased occupancy on ERV promoters and inhibition of two major ERV repressors, histone demethylase LSD1 and DNA methyltransferase DNMT1. Double-stranded RNA stress caused by ERVs triggered type I/III interferon expression and antigen processing and presentation. Pharmacologic activation of p53 in vivo unleashed the IFN program, promoted T-cell infiltration, and significantly enhanced the efficacy of checkpoint therapy in an allograft tumor model. Furthermore, the MDM2 inhibitor ALRN-6924 induced a viral mimicry pathway and tumor inflammation signature genes in patients with melanoma. Our results identify ERV expression as the central mechanism whereby p53 induction overcomes tumor immune evasion and transforms tumor microenvironment to a favorable phenotype, providing a rationale for the synergy of MDM2 inhibitors and immunotherapy.

SIGNIFICANCE

We found that p53 activated by MDM2 inhibitors induced the expression of ERVs, in part via epigenetic factors LSD1 and DNMT1. Induction of IFN response caused by ERV derepression upon p53-targeting therapies provides a possibility to overcome resistance to immune checkpoint blockade and potentially transform "cold" tumors into "hot." This article is highlighted in the In This Issue feature, p. 2945.

Phase 1 Trial of ALRN-6924, a Dual Inhibitor of MDMX and MDM2, in Patients with Solid Tumors and Lymphomas Bearing Wild-type TP53

PURPOSE

We describe the first-in-human dose-escalation trial for ALRN-6924, a stabilized, cell-permeating peptide that disrupts p53 inhibition by mouse double minute 2 (MDM2) and MDMX to induce cell-cycle arrest or apoptosis in TP53-wild-type (WT) tumors.

PATIENTS AND METHODS

Two schedules were evaluated for safety, pharmacokinetics, pharmacodynamics, and antitumor effects in patients with solid tumors or lymphomas. In arm A, patients received ALRN-6924 by intravenous infusion once-weekly for 3 weeks every 28 days; arm B was twice-weekly for 2 weeks every 21 days.

RESULTS

Seventy-one patients were enrolled: 41 in arm A (0.16-4.4 mg/kg) and 30 in arm B (0.32-2.7 mg/kg). ALRN-6924 showed dose-dependent pharmacokinetics and increased serum levels of MIC-1, a biomarker of p53 activation. The most frequent treatment-related adverse events were gastrointestinal side effects, fatigue, anemia, and headache. In arm A, at 4.4 mg/kg, dose-limiting toxicities (DLT) were grade 3 (G3) hypotension, G3 alkaline phosphatase elevation, G3 anemia, and G4 neutropenia in one patient each. At the MTD in arm A of 3.1 mg/kg, G3 fatigue was observed in one patient. No DLTs were observed in arm B. No G3/G4 thrombocytopenia was observed in any patient. Seven patients had infusion-related reactions; 3 discontinued treatment. In 41 efficacy-evaluable patients with TP53-WT disease across both schedules the disease control rate was 59%. Two patients had confirmed complete responses, 2 had confirmed partial responses, and 20 had stable disease. Six patients were treated for >1 year. The recommended phase 2 dose was schedule A, 3.1 mg/kg.

CONCLUSIONS

ALRN-6924 was well tolerated and demonstrated antitumor activity.

First in class dual MDM2/MDMX inhibitor ALRN-6924 enhances antitumor efficacy of chemotherapy in TP53 wild-type hormone receptor-positive breast cancer models

BACKGROUND

MDM2/MDMX proteins are frequently elevated in hormone receptor-positive (ER+) breast cancer. We sought to determine the antitumor efficacy of the combination of ALRN-6924, a dual inhibitor of MDM2/MDMX, with chemotherapy in ER+ breast cancer models.

METHODS

Three hundred two cell lines representing multiple tumor types were screened to confirm the role of TP53 status in ALRN-6924 efficacy. ER+ breast cancer cell lines (MCF-7 and ZR-75-1) were used to investigate the antitumor efficacy of ALRN-6924 combination. In vitro cell proliferation, cell cycle, and apoptosis assays were performed. Xenograft tumor volumes were measured, and reverse-phase protein array (RPPA), immunohistochemistry (IHC), and TUNEL assay of tumor tissues were performed to evaluate the in vivo pharmacodynamic effects of ALRN-6924 with paclitaxel.

RESULTS

ALRN-6924 was active in wild-type TP53 (WT-TP53) cancer cell lines, but not mutant TP53. On ER+ breast cancer cell lines, it was synergistic in vitro and had enhanced in vivo antitumor activity with both paclitaxel and eribulin. Flow cytometry revealed signs of mitotic crisis in all treatment groups; however, S phase was only decreased in MCF-7 single agent and combinatorial ALRN-6924 arms. RPPA and IHC demonstrated an increase in p21 expression in both combinatorial and single agent ALRN-6924 in vivo treatment groups. Apoptotic assays revealed a significantly enhanced in vivo apoptotic rate in ALRN-6924 combined with paclitaxel treatment arm compared to either single agent.

CONCLUSION

The significant synergy observed with ALRN-6924 in combination with chemotherapeutic agents supports further evaluation in patients with hormone receptor-positive breast cancer.

Abstract C064: The investigational peptide drug ALRN-6924, a dual inhibitor of MDMX and MDM2, is an effective myelopreservation agent

Aim: We investigated whether p53 activation with ALRN-6924 can prevent or reduce chemotherapy-induced hematopoietic toxicity while preserving or enhancing anti-tumor efficacy of chemotherapy in p53-mutant tumors. Materials and methods: ALRN-6924 is a clinical-stage, first-in-class, stabilized cell-permeating alpha-helical peptide that disrupts the interaction of the p53 tumor suppressor protein with its endogenous inhibitors, MDMX and MDM2. For p53 wild-type cells such as normal bone marrow, p53 activation can induce transient, dose-dependent cell cycle arrest, reducing sensitivity to chemotherapy-induced cellular toxicity. For p53-mutant cancer cells, ALRN-6924 has no effect on the cell cycle, leaving them vulnerable to chemotherapy. ALRN-6924-induced cell cycle arrest was measured by flow cytometry in human bone marrow CD34+ cells following incubation with ALRN-6924 ex vivo for 24 hours. DNA synthesis and DNA content were quantified by flow cytometry using EdU incorporation and Hoechst 33342 staining, respectively. Cell cycle arrest in the bone marrow of ALRN-6924-treated C57BL/6 mice was measured by flow cytometry using EdU incorporation in lineage negative, Kit positive hematopoietic stem and progenitor cells. Topotecan-induced DNA damage was measured in human bone marrow CD34+ cells by H2γX incorporation following exposure to vehicle or ALRN-6924 for 24 hours to induce cell cycle arrest, then incubated with topotecan for an additional 24 hours following a wash-out step. Topotecan-induced neutropenia was measured in female C57BL/6 mice following topotecan treatment on days 1-5 and either ALRN-6924 or vehicle on days 0-4. Female C57BL/6 mice bearing subcutaneous p53-mutant MC38 syngeneic tumors were treated with ALRN-6924, vehicle and topotecan on the same dosing regimen and followed until tumors reached >1000mm3. Results: ALRN-6924 induces transient, reversible cell cycle arrest in bone marrow cells in vitro and in vivo, and protects human bone marrow cells against topotecan-induced DNA damage ex vivo. In a mouse model of topotecan-induced neutropenia, ALRN-6924 protected against neutrophil depletion when daily administration started 24 hours prior to the 1st dose and 30 minutes before each subsequent dose of topotecan. ALRN-6924 does not diminish topotecan’s anti-tumor activity in the p53-mutant MC38 syngeneic mouse cancer model, with the ALRN-6924 + topotecan combination yielding modest enhancement of survival. Body weights and mortality data suggest ALRN-6924 and combinations with topotecan were tolerated at the doses tested. Conclusions: ALRN-6924 reduces chemotherapy-induced hematopoietic toxicity in healthy human bone marrow cells ex vivo and in mouse models of topotecan-induced neutropenia in vivo, while preserving or enhancing anti-tumor efficacy in p53-mutant tumors when administered intravenously prior to chemotherapy. These results support the first ALRN-6924 clinical trial for myelopreservation in topotecan-treated small-cell lung cancer patients (NCT04022876). Additional studies are underway to support ALRN-6924 as a tumor type-agnostic myelopreservation agent for cancer patients with tumors bearing p53 mutations who are treated with chemotherapy.

Citation Format: Luis A Carvajal, David Sutton, Mariam Mounir, Joseph McClanaghan, Vincent Guerlavais, Manuel Aivado, Vojislav Vukovic, Allen Annis. The investigational peptide drug ALRN-6924, a dual inhibitor of MDMX and MDM2, is an effective myelopreservation agent [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C064. doi:10.1158/1535-7163.TARG-19-C064

Dual inhibition of MDMX and MDM2 as a therapeutic strategy in leukemia

The tumor suppressor p53 is often inactivated via its interaction with endogenous inhibitors mouse double minute 4 homolog (MDM4 or MDMX) or mouse double minute 2 homolog (MDM2), which are frequently overexpressed in patients with acute myeloid leukemia (AML) and other cancers. Pharmacological disruption of both of these interactions has long been sought after as an attractive strategy to fully restore p53-dependent tumor suppressor activity in cancers with wild-type p53. Selective targeting of this pathway has thus far been limited to MDM2-only small-molecule inhibitors, which lack affinity for MDMX. We demonstrate that dual MDMX/MDM2 inhibition with a stapled α-helical peptide (ALRN-6924), which has recently entered phase I clinical testing, produces marked antileukemic effects. ALRN-6924 robustly activates p53-dependent transcription at the single-cell and single-molecule levels and exhibits biochemical and molecular biological on-target activity in leukemia cells in vitro and in vivo. Dual MDMX/MDM2 inhibition by ALRN-6924 inhibits cellular proliferation by inducing cell cycle arrest and apoptosis in cell lines and primary AML patient cells, including leukemic stem cell-enriched populations, and disrupts functional clonogenic and serial replating capacity. Furthermore, ALRN-6924 markedly improves survival in AML xenograft models. Our study provides mechanistic insight to support further testing of ALRN-6924 as a therapeutic approach in AML and other cancers with wild-type p53.

Abstract P6-21-07: The stapled peptide ALRN-6924, a dual inhibitor of MDMX and MDM2, and the CDK4/6 inhibitors palbociclib or abemaciclib synergistically enhance each other's in vitro and in vivo anticancer activity

Background ALRN-6924 is a cell-penetrating α-helical stapled peptide that disrupts the interaction of the p53 tumor suppressor protein and its inhibitors, MDMX and MDM2. Reactivation of p53 with ALRN-6924 in TP53-wild-type tumors triggers cell cycle arrest and apoptosis resulting in antitumor efficacy. CDK4/6 inhibitors induce apoptosis, senescence, and cell growth arrest via the interrelated Rb pathway, and co-amplification of MDM2 and CDK4 (both on chromosome 12q13) is a known oncogenic driver, suggesting that combinations of ALRN-6924 and CDK4/6i's may be synergistic. This study evaluates the antitumor efficacy and pharmacodynamics (PD) of ALRN-6924 combined with palbociclib or abemaciclib.

Methods ALRN-6924 was tested in combination with palbociclib or abemaciclib in MCF-7 breast cancer cell lines and MDM2- and CDK4-co-amplified SJSA-1 sarcoma cell lines using WST-1 cell viability assays. Synergy was quantified by the Chou-Talalay combination index method. Single agents and combinations were evaluated in cell culture using assays for apoptosis (Caspase 3/7 cleavage), proliferation (BrdU), senescence (ß-Galactosidase), colony growth (Giemsa), and Western blot analysis of p53, p21, Rb, phospho-Rb, FOXM1, and phospho-FOXM1; and E2F1 mRNA. In vivo combinations were tested in athymic nude mouse MCF-7 and SJSA-1 xenograft models, with cell cycle assays (EdU) measured in tumor samples by flow cytometry.

Results ALRN-6924 combinations with palbociclib or abemaciclib display synergistic in vitro anti-proliferative activity in MCF-7 and SJSA-1 cells. ALRN-6924 induces senescence in vitro as a monotherapy and in combination with CDK4/6i's. Western blot assays show that ALRN-6924/palbociclib combinations trigger sustained on-mechanism biomarker activation, vs. transient activation with single agents. Phospho-Rb and phospho-FOXM1 down-regulation, p53 and p21 up-regulation, and repression of E2F1 mRNA are sustained after wash-out in combination, but not in single agent-treated cells. MCF-7 and SJSA-1 tumor growth inhibition was improved in mice treated with ALRN-6924 combinations with either palbociclib or abemaciclib vs. single agent. EdU assays show that ALRN-6924/palbociclib combinations inhibit SJSA-1 tumor cell proliferation in vivo. Body weights and mortality data show the combination of ALRN-6924 with palbociclib 75 mg/kg/day was well tolerated; the combination with abemaciclib 100 mg/kg/day was tolerated with interruption and dose-reduction. No pharmacokinetic (PK) drug-drug interactions were noted in nude mice due to different modes of metabolism for ALRN-6924 (proteolysis) and palbociclib (CYP3A).

Conclusions This study demonstrates that ALRN-6924 and CDK4/6i combinations show synergistic activity. PD biomarkers indicate on-mechanism in vitro activity that is sustained after wash-out. In vivo efficacy, biomarker, PK, and tolerability results, plus clinical evidence that the most frequent and concerning safety issues for CDK4/6i's (neutropenia, leukopenia, infections) do not overlap with ALRN-6924's reported safety profile (Meric-Bernstam et al., ASCO 2017) support the development of combination regimens for breast cancer and other malignancies.

Citation Format: Annis A, Carvajal LA, Ren J-G, Sutton D, Santiago S, Narasimhan N, Guerlavais V, Aivado M. The stapled peptide ALRN-6924, a dual inhibitor of MDMX and MDM2, and the CDK4/6 inhibitors palbociclib or abemaciclib synergistically enhance each other's in vitro and in vivo anticancer activity [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-21-07.

Abstract P6-20-11: The stapled peptide ALRN-6924, a dual inhibitor of MDMX and MDM2, enhances antitumor efficacy of paclitaxel and Nab-paclitaxel in TP53 wild-type MCF-7 breast cancer models

Background: MDMX and MDM2 are endogenous inhibitors of the p53 tumor suppressor protein. MDMX levels are frequently elevated in luminal breast cancer, which generally expresses wild-type p53. ALRN-6924, an α-helical stapled peptide, is the first and only dual inhibitor of MDMX and MDM2 currently in clinical trials for solid tumors and hematological malignancies. We sought to determine the antitumor efficacy of the combination of ALRN-6924 with taxanes in models of human breast cancer.

Methods: Sulforhodamine B colorimetric assay was used to assess the cytotoxicity of the combination of ALRN-6924 with taxanes in vitro. Athymic nude mice were implanted with MCF-7 tumors and treated for four weeks with ALRN-6924 alone and in combination with paclitaxel in cremaphor (Taxol®, study #1) or a nanoparticle-albumin-bound (nab) formulation (Abraxane®, study #2). In study #1, ALRN-6924 (5, 10 mg/kg) was dosed twice weekly and paclitaxel (10, 15 mg/kg) was dosed weekly, with paclitaxel administered 6 h prior to ALRN-6924. In study #2, ALRN-6924 alone (5 mg/kg) was dosed twice weekly while nab-paclitaxel (15 mg/kg) was administered weekly in combination at -24h, -6h, 0h, +6h, or +24h relative to ALRN-6924 administration.

Results: ALRN-6924 was found to have synergistic activity with paclitaxel in both MCF-7 and ZR-75-1 cell lines in vitro (Combination index: 0.874 and 0.323 respectively). In in vivo study #1, the combination of ALRN-6924 and paclitaxel significantly inhibited MCF-7 tumor growth compared to either agent alone (p<0.005). Paclitaxel 15 mg/kg + ALRN-6924 5 mg/kg resulted in the greatest tumor inhibition with average tumor size decreased by 13% at four weeks versus the starting size.

In study #2, the combination of nab-paclitaxel with ALRN-6924 administered -6h to +24h relative to nab-paclitaxel resulted in improved efficacy over either single agent and a significant increase in the number of tumor regressions (up to 6/10 with 3 consecutive measurements <50% of starting volume) compared to nab-paclitaxel alone (1/10, p<0.005). When ALRN-6924 was administered 24h prior to nab-paclitaxel, there was a marked decrease in efficacy and no tumor regressions were observed.

In both studies, drug treatments were well tolerated with no significant weight loss in mice.

Conclusion: The significant increase in efficacy observed with ALRN-6924 in combination with paclitaxel supports further evaluation in patients with breast cancer.

Citation Format: Pairawan SS, Yuca E, Evans K, Annis A, Narasimhan N, Sutton D, Carvajal LA, Ren J-G, Santiago S, Guerlavais V, Akcakanat A, Tapia C, Illeana Dumbrava EE, Aivado M, Meric-Bernstam F. The stapled peptide ALRN-6924, a dual inhibitor of MDMX and MDM2, enhances antitumor efficacy of paclitaxel and Nab-paclitaxel in TP53 wild-type MCF-7 breast cancer models [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-20-11.

Phase I trial of a novel stapled peptide ALRN-6924 disrupting MDMX- and MDM2-mediated inhibition of WT p53 in patients with solid tumors and lymphomas

2505

Background: ALRN-6924 is a cell-penetrating stapled alpha-helical peptide designed to equipotently disrupt the interaction between the p53 tumor suppressor protein and its endogenous inhibitors, murine double minute X (MDMX) and 2 (MDM2). For TP53 wild-type (WT) tumors, pharmacological disruption of this interaction offers a means to restore p53-dependent cell cycle arrest and apoptosis, resulting in antitumor efficacy via a novel mechanism. Methods: The study evaluated safety, PK, PD and anti-tumor effects of ALRN-6924 in patients (pts) with advanced solid tumors or lymphomas in a standard 3+3 design. Pts received ALRN-6924 IV once weekly for 3 consecutive wks on a 28-day cycle (arm A), or 2/wk for 2 consecutive wks on a 21-day cycle (arm B). Results: As of Dec 2016, 69 pts were enrolled with median age 61 yrs (25-78). Pts received a median of 2 (1-19) cycles in arm A [0.16-4.4 mg/kg] and 3 (1-19) cycles in arm B [0.32-2.7 mg/kg]. ALRN-6924 showed a t1/2 of 5.5 hours, dose-dependent PK, and an increase in serum macrophage inhibitory cytokine-1. Treatment-related AEs seen in 96% of pts were primarily grade 1 and 2; most frequent were GI side effects, fatigue, anemia, and headache. DLTs were G3 fatigue at 3.1 mg/kg, and G3 hypotension, G3 alkaline phosphatase elevation, G3 anemia and G4 neutropenia at 4.4 mg/kg all in 5 pts in arm A. No G3/4 thrombocytopenia was observed. All DLTs resolved with dose hold. Infusion-related reactions were seen in 7 pts, with 3 treatment discontinuations. The RP2D was determined to be at MTD: 3.1 mg/kg QW for 3 wks every 28 days. In 55 pts evaluable for efficacy, disease control rate (DCR) was 45%, including 2 CR (Peripheral T-cell Lymphoma [PTCL], Merkel Cell Carcinoma), 2 PRs (Colorectal Cancer, Liposarcoma) and 21 pts with SD. In WT TP53 pts who initiated ALRN-6924 at ≥0.8 mg/kg, DCR was 57%. 9 pts remain on treatment post data cutoff including 3 pts exceeding 1 year of treatment. Conclusions: ALRN-6924 was well tolerated and demonstrated intriguing anti-tumor activity in this first-in-human phase I trial. An expansion phase IIa cohort in PTCL opened in August 2016 using 3.1 mg/kg (arm A) and is currently enrolling. Clinical trial information: NCT02264613.

Macrocyclic α-Helical Peptide Drug Discovery

Macrocyclic α-helical peptides have emerged as a promising new drug class and within the scope of hydrocarbon-stapled peptides such molecules have advanced into the clinic. The overarching concept of designing proteomimetics of an α-helical ‘ligand’ which binds its cognate ‘target’ relative to α-helical interfacing protein-protein interactions has been well-validated and expanded through numerous investigations for a plethora of therapeutic targets oftentimes referred to as “undruggable” with respect to other modalities (e.g., small-molecule or proteins). This chapter highlights the evolution of macrocyclic α-helical peptides in terms of target space, biophysical and computational chemistry, structural diversity and synthesis, drug design and chemical biology. It is noteworthy that hydrocarbon-stapled peptides have successfully risen to the summit of such drug discovery campaigns.

Abstract LB-304: ATSP-9172, a novel Stapled Peptide inhibitor of HIF-dependent transcriptional activity with in vivo antitumor efficacy in a preclinical model of prostate cancer

Hypoxia-inducible transcription factors (HIF) are key regulators of cellular adaptation to hypoxia in solid tumors, and HIF-1α controls the expression of genes involved in anaerobic metabolism, angiogenesis, cell growth and survival. Hydrocarbon cross-linked alpha helical peptides (Stapled Peptides) are a breakthrough approach to create new class of drugs that modulate intracellular protein-protein interactions. Here, we have mimicked the structure and function of the CITED2 protein, an endogenous negative regulator of the interaction between HIF-1α and p300 proteins, by designing a Stapled Peptide derived from CITED2 to generate the first example of a potent and selective Stapled Peptide inhibitor of HIF-1α-dependent transcription. ATSP-9172 bound to the CH1 domain of p300 and disrupted the HIF-1α C-TAD/CH1 interaction in biochemical assays and inhibited HIF-dependent reporter gene activity in ME-180 cells. Examination of endogenous transcript levels in ME-180 cells revealed that ATSP-9172 down-regulated the transcription of HIF-1α target genes, such as adolase C, angiopoietin-like 4, and carbonic anhydrase 9 in a dose-dependent manner, but did not affect the expression of non-HIF target genes, verifying a specific and on-target mechanism of action. ATSP-9172 exhibited a dramatic improvement in solubility and plasma stability profile relative to the linear peptide, and demonstrated favorable pharmacokinetic properties in mice by providing high systemic exposure, low plasma clearance and long elimination half-life. Finally, intravenous administration of ATSP-9172 on an every other day schedule significantly inhibited tumor growth in a PC-3 human prostate tumor xenograft model (p < 0.05); this inhibition was found to be dose-dependent. Our results demonstrate that a Stapled Peptide mimicking the HIF inhibitory function of the native CITED2 protein provides a novel and specific strategy to suppress HIF-1α-dependent gene expression for cancer therapy.

Citation Format: Kaiming Sun, Steven J. DeMarco, Vincent Guerlavais, Aditi Mukherjee, Sean Irwin, Eric Shi, Hongliang Cai, Krzysztof Darlak, Solimar Santiago, Jessica Pero, Karen A. Olson, Huw M. Nash, Yong Chang. ATSP-9172, a novel Stapled Peptide inhibitor of HIF-dependent transcriptional activity with in vivo antitumor efficacy in a preclinical model of prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-304. doi:10.1158/1538-7445.AM2013-LB-304

Formation of multiple complexes between beta-dystroglycan and dystrophin family products

Beta-dystroglycan is expressed in a wide variety of tissues and has generally been reported with an Mr of 43 kDa, sometimes accompanied with a 31 kDa protein assumed to be a truncated product. This molecule was recently identified as the anomalous beta-dystroglycan expressed in various carcinoma cell lines. We produced and characterized a G5 polyclonal antibody specific to beta-dystroglycan that is directed against the C-terminal portion of the molecule. We provide evidence that beta-dystroglycan may vary in size and properties by studying different Xenopus tissues. Besides normal beta-dystroglycan with an Mr of 43 kDa in smooth and cardiac muscle and sciatic nerve extracts, we found it in skeletal muscle and brain proteins with an Mr of 38 and 65 kDa, respectively. Glycosylation properties and proteolytic susceptibilities of these different beta-dystroglycans are analysed and compared in this work. Crosslinking experiments with various beta-dystroglycan preparations obtained from skeletal and cardiac muscles and brain gave rise to specific new covalent products with Mr of 125 kDa (doublet band), or 120 and 130 kDa, or 140 and 240 kDa, respectively. We provide evidence, using various similar beta-dystroglycan preparations, that the immunoprecipitation procedure with G5 specific polyclonal antibody allows consistent pelleting of various dystrophin-family isoforms. Skeletal muscles from Xenopus reveals the presence of two distinct beta-dystroglycan complexes, one with dystrophin and another one which involves alpha-dystrobrevin. Cardiac muscle and brain from Xenopus are shown to contain three beta-dystroglycan complexes related to various dystrophin-family isoforms. Dystrophin or alpha-dystrobrevin or Dp71 were found in cardiac muscle and dystrophin or Dp180 or Up71 in brain. This variability in the relationship between beta-dystroglycan and dystrophin-family isoforms suggests that each protein--currently known as dystrophin associated protein--could not be present in each of these complexes.

Dystrophin and dystrophin-associated protein in muscles and nerves from monkey

Since all organs (i.e. skeletal, cardiac, smooth muscles and sciatic nerve) are never only taken from a single patient, all these tissues were obtained from one cynomolgus monkey, a model closely resembling humans. This work describes an up-to-date reinvestigation of the dystrophin-glycoprotein complex and related molecules in various monkey tissues such those cited above. We used monoclonal and polyclonal antibodies produced in our laboratory, which are directed against dystrophin, utrophin, short-dystrophin products, alpha-dystrobrevin, beta-dystroglycan, alpha-syntrophin, alpha-, beta-, gamma-, delta-, epsilon-sarcoglycan, and sarcospan. For each molecule, we determined their molecular weight and tissue localization. Regardless of the tissue analyzed, at least one dystrophin or utrophin as full-length molecule and one short-dystrophin product or dystrobrevin as proteins belonging to the dystrophin superfamily were found. Beta-dystroglycan, beta and delta sarcoglycans were always detected, while other sarcoglycans varied from all to only three components. Epsilon sarcoglycan appears to be specific to smooth muscle, which is devoid of alpha sarcoglycan. Sarcospan is only absent from sciatic nerve structures. Among the different muscles investigated in this study, short dystrophin products are only present in cardiac muscle. All of these findings are summarized in one table, which highlight in one single animal the variability of the dystrophin-glycoprotein complex components in relation with the organ studied. This statement is important because any attempt to estimate protein restoration needs in each study the knowledge of the expected components that should be considered normal.

New active series of growth hormone secretagogues

New growth hormone secretagogue (GHS) analogues were synthesized and evaluated for growth hormone releasing activity. This series derived from EP-51389 is based on a gem-diamino structure. Compounds that exhibited higher in vivo GH-releasing potency than hexarelin in rat (subcutaneous administration) were then tested per os in beagle dogs and for their binding affinity to human pituitary GHS receptors and to hGHS-R 1a. Compound 7 (JMV 1843, H-Aib-(d)-Trp-(d)-gTrp-formyl) showed high potency in these tests and was selected for clinical studies.(1)

EP1572: a novel peptido-mimetic GH secretagogue with potent and selective GH-releasing activity in man

EP1572 UMV1843 [Aib-DTrp-DgTrp-CHO]) is a new peptido-mimetic GH secretagogue (GHS) showing binding potency to the GHS-receptor in animal and human tissues similar to that of ghrelin and peptidyl GHS. EP1572 induces marked GH increase after s.c. administration in neonatal rats. Preliminary data in 2 normal young men show that: 1) acute i.v. EP1572 administration (1.0 microg/kg) induces strong and selective increase of GH levels; 2) single oral EP1572 administration strongly and reproducibly increases GH levels even after a dose as low as 0.06 mg/kg. Thus, EP1572 is a new peptido-mimetic GHS with potent and selective GH-releasing activity.

Growth hormone secretagogues: past, present and future

Growth hormone-releasing peptides (GHRPs) or growth hormone secretagogues (GHSs) of peptide or non-peptide structure are able to stimulate growth hormone secretion. They act through a growth hormone-releasing hormone (GHRH)/somatotropin release inhibiting factor (SRIF) independent pathway. A receptor able to bind to these compounds was cloned in 1996, and a natural ligand of this receptor, named ghrelin, was characterized in 1999. The potential therapeutic value of such compounds is considerable as they offer an alternative therapy for treatment of deficiency in growth hormone secretion. As growth hormone (GH) also participates in many anabolic effects, interest in these compounds is increasing and many clinical applications are expected in the future.