Protein Epitope Mimetics Technology Research Articles

ET-51 * COMBINED THERAPY WITH A NOVEL CXCR4 ANTAGONIST AND AN ANTI-VEGF ANTIBODY IMPAIRS THE GROWTH OF GLIOMAS

BACKGROUND: Expression of chemokine receptor CXCR4 and its ligand stromal cell-derived factor-1α (SDF-1α) is enhanced in glioblastoma, including at invasive edges, and associated with proliferation, invasion and angiogenesis (Zagzag, 2008; Ehtesham, 2013; Gagliardi, 2014). Using Protein Epitope Mimetics technology (Robinson, 2008), Polyphor Ltd. has developed selective, highly potent CXCR4 antagonists (De Marco, 2006), e.g., POL5551 (Ki: 0.5 nM). To address the problem of resistance to antiangiogenic therapy, we sought to determine whether POL5551 could inhibit the growth and/or invasion of gliomas in vivo. METHODS: Female adult C57BL/6 mice were implanted orthotopically with 1 x 105 CT-2A or GL261 glioma cells. On day 14, mice were randomized into 4 groups: 1) control, 2) POL5551 (5 mg/kg s.c.) twice daily, 3) anti-murine VEGF monoclonal antibody B20-4.1.1 (Genentech Inc.) (5 mg/kg i.p.) twice weekly (Bagri, 2010) and 4) combined POL5551 and B20-4.1.1. On day 28, brain tissues were processed, sections analyzed for tumor volume and invasion (HE 45.8 nM) than in brain adjacent to tumor (45 ± 4.8; 23.7) or normal brain (21 ± 1.5; 11.1) and sufficient to account for its biological effects. CONCLUSIONS: Although combined therapy did not reduce significantly glioma invasion, it did impair the growth of CT-2A and GL261 gliomas by 69.8% and 59.9%, respectively. Our results suggest the potential utility of POL5551 as adjunct therapy for glioblastoma.

The novel CXCR4 antagonist POL5551 mobilizes hematopoietic stem and progenitor cells with greater efficiency than Plerixafor.

Mobilized blood has supplanted bone marrow (BM) as the primary source of hematopoietic stem cells for autologous and allogeneic stem cell transplantation. Pharmacologically enforced egress of hematopoietic stem cells from BM, or mobilization, has been achieved by directly or indirectly targeting the CXCL12/CXCR4 axis. Shortcomings of the standard mobilizing agent, granulocyte colony-stimulating factor (G-CSF), administered alone or in combination with the only approved CXCR4 antagonist, Plerixafor, continue to fuel the quest for new mobilizing agents. Using Protein Epitope Mimetics technology, a novel peptidic CXCR4 antagonist, POL5551, was developed. In vitro data presented herein indicate high affinity to and specificity for CXCR4. POL5551 exhibited rapid mobilization kinetics and unprecedented efficiency in C57BL/6 mice, exceeding that of Plerixafor and at higher doses also of G-CSF. POL5551-mobilized stem cells demonstrated adequate transplantation properties. In contrast to G-CSF, POL5551 did not induce major morphological changes in the BM of mice. Moreover, we provide evidence of direct POL5551 binding to hematopoietic stem and progenitor cells (HSPCs) in vivo, strengthening the hypothesis that CXCR4 antagonists mediate mobilization by direct targeting of HSPCs. In summary, POL5551 is a potent mobilizing agent for HSPCs in mice with promising therapeutic potential if these data can be corroborated in humans.

First Results of a Phase-II Study with the New CXCR4 Antagonist POL6326 to Mobilize Hematopoietic Stem Cells (HSC) In Multiple Myeloma (MM)

AbstractAbstract 824In multiple myeloma (MM), the second most common hematological malignancy, high-dose therapy followed by autologous CD34+ stem cell transplantation (ABSCT) is therapy of choice for younger patients. Standard treatment to mobilize hematopoietic stem cells (HSC) is either G-CSF alone or combined with chemotherapy. In the last years the antagonism of the CXCR4 receptor has been identified as a potent mechanism of HSC release from the bone marrow compartment. This mobilization by CXCR4 antagonists is more direct and more rapid than by G-CSF given over 4 to 6 days, and the combination of G-CSF plus a CXCR4 antagonist is superior to G-CSF alone. Furthermore, HSC mobilized using G-CSF and a CXCR4 antagonist have been shown to result in a rapid and sustained engraftment post-transplantation.POL6326 is a novel, potent and selective CXCR4 antagonist based on the PEM (Protein Epitope Mimetics) technology for intravenous application. In a previous Phase I study in 52 healthy volunteers POL6326 has been demonstrated to effectively mobilize CD34+ stem cells and was very well tolerated.The goal of the Phase II study in newly diagnosed myeloma patients reported here was to test to what extent POL6326 can be used as monotherapy, infused over 1 or 2h, to mobilize sufficient HSC for subsequent autologous transplantation. In our study the minimum number of HSC required for ABSCT was 2 × 106 CD34+ cells/kg body weight (BW). All patients also received CAD/G-CSF (cyclophosphamide, doxorubicin and dexamethasone) about 10 days after POL6326 and leukapheresis.The second goal was to determine tumour cell mobilization by polymerase chain-reaction after POL6326 or CAD/G-CSF respectively.Here we report the first data of this ongoing study. In all doses tested, up to 1200 μg/kg BW over 2h, POL6326 was safe and very well tolerated. During a total number of 38 infusions the only minor adverse event possibly related to study drug was a discrete pruritus of CTC grade 1 at the infusion site during POL6326 administration on two consecutive days. It resolved spontaneously and did not require any medication. This excellent safety and tolerability profile warrants further dose escalation in the ongoing trial.After first diagnosis, patients received 3 cycles of induction chemotherapy with bortezomib (or thalidomide respectively in one single subject) plus doxorubicin and dexamethasone. 3 weeks after the last injection of induction treatment HSC were mobilized with POL6326 given as a 1 or 2h infusion on up to 4 consecutive days according to an intra-individual dose escalation scheme (from 600 to 1200 μg/kg) with consecutive leukapheresis 30 min after end of infusion.In all patients (n=16) we observed an elevation of leukocytes and HSC compared to baseline. In 66% of patients sufficient stem cells were mobilized with POL6326 for ABSCT (with a mean of 2.5 × 106 CD34+ cells/kg BW). In 75 % of these subjects 2 leukapheresis cycles were sufficient to reach the minimum number of HSC.In all patients undergoing ABSCT with HSC mobilized by POL6326, the engraftment was successful. The time to reconstitution ranged from 10 to 19 days (mean 14 days) and was comparable to ABSCT with CAD/G-CSF-mobilized HSC (historical mean of 14 days and a range from 6 to 31 days).Five patients were evaluated for the presence of tumour cells in peripheral blood before mobilization and in leukapheresis products after treatment with POL6326 and CAD/G-CSF. In 2 of these patients we could not detect any tumour cells, neither in all leukapheresis products nor in all peripheral blood samples. In 2 patients a minor contamination with less than 0.0001% of tumour cells was detected both in the peripheral blood before POL6326 and in the leukapheresis products. Finally, 1 patient showed a similarly minor (<0.0001%) percentage of tumour cells only in the apheresis product after POL6326 treatment. However, a significant mobilization of tumour cells (0.001%) was detected after CAD plus G-CSF in this patient.Due to the excellent safety and tolerability profile observed for POL6326 in this study the next steps include further dose escalation. These initial data with low doses of POL6326 indicate that this novel CXCR4 antagonist holds the promise to be eventually used as a stand alone therapy not requiring the application of G-CSF. The preliminary findings of the absence or very low counts of tumour cells in the leukapheresis product generated with POL6326 warrant further investigation. Disclosures:Off Label Use: POL6326 as new CXCR4 antagonist for experimental CD34+ hematopoietic stem cell mobilization. Dembowsky:Polyphor Ltd: Employment. Braun:Cytonet Heidelberg GmbH: Employment. Ludin:Polyphor Ltd: Employment.

Recent Progress in the Discovery of Macrocyclic Compounds as Potential Anti-Infective Therapeutics

Novel therapeutic strategies are urgently needed for the treatment of serious diseases caused by viral, bacterial and parasitic infections, because currently used drugs are facing the problem of rapidly emerging resistance. There is also an urgent need for agents that act on novel pathogen-specific targets, in order to expand the repertoire of possible therapies. The high throughput screening of diverse small molecule compound libraries has provided only a limited number of new lead series, and the number of compounds acting on novel targets is even smaller. Natural product screening has traditionally been very successful in the anti-infective area. Several successful drugs on the market as well as other compounds in clinical development are derived from natural products. Amongst these, many are macrocyclic compounds in the 1-2 kDa size range. This review will describe recent advances and novel drug discovery approaches in the anti-infective area, focusing on synthetic and natural macrocyclic compounds for which in vivo proof of concept has been established. The review will also highlight the Protein Epitope Mimetics (PEM) technology as a novel tool in the drug discovery process. Here the structures of naturally occurring antimicrobial and antiviral peptides and proteins are used as starting points to generate novel macrocyclic mimetics, which can be produced and optimized efficiently by combinatorial synthetic methods. Several recent examples highlight the great potential of the PEM approach in the discovery of new anti-infective agents.

The design, structures and therapeutic potential of protein epitope mimetics

Using a biologically relevant peptide or protein structure as a starting point for lead identification represents one of the most powerful approaches in modern drug discovery. Here, we focus on the protein epitope mimetic (PEM) approach, where folded 3D structures of peptides and proteins are taken as starting points for the design of synthetic molecules that mimic key epitopes involved in protein-protein and protein-nucleic acid interactions. By transferring the epitope from a recombinant to a synthetic scaffold that can be produced by parallel combinatorial methods, it is possible to optimize target affinity and specificity as well as other drug-like ADMET properties. The PEM technology is a powerful tool for target validation, and for the development of novel PEM-based drugs.

Discovery of Highly Potent and Selective CXCR4 Inhibitors Using Protein Epitope Mimetics (PEM) Technology

Novel, highly potent CXCR4 inhibitors with good pharmacokinetic properties were obtained by applying PEM technology starting from the naturally occurring ?-hairpin peptide polyphemusin II. The design involved incorporation of key residues from polyphemusin II into a macrocyclic template-bound ?-hairpin mimetic. Using a parallel synthesis approach, the potency and ADME properties of the mimetics were optimized, resulting in CXCR4 inhibitors such as POL2438 and POL3026. Their activities were confirmed in a series of in vitro HIV-1 infection assays. Besides high selectivity for CXCR4, POL3026 had excellent plasma stability and favorable pharmacokinetic properties in dogs. In a murine model POL3026 was highly efficacious in hematopoietic stem cell mobilization. Hence, PEM-based CXCR4 inhibitors have the potential to become therapeutic agents for the treatment of HIV infections (as entry inhibitor), cancer (e.g. for inhibition of metastasis), stem cell transplant and inflammation.