Roberto Costante

Biological Active Analogues of the Opioid Peptide Biphalin: Mixed α/β3-Peptides

Natural residues of the dimeric opioid peptide Biphalin were replaced by the corresponding homo-β(3) amino acids. The derivative 1 containing hβ(3) Phe in place of Phe showed good μ- and δ-receptor affinities (Ki(δ) = 0.72 nM; Ki(μ) = 1.1 nM) and antinociceptive activity in vivo together with an increased enzymatic stability in human plasma.

Exploring new Probenecid-based carbonic anhydrase inhibitors: Synthesis, biological evaluation and docking studies

Novel Probenecid-based amide derivatives, incorporating different natural amino acids, were synthesized and assayed to test their effect on the human carbonic anhydrase (hCA, EC 4.2.1.1) transmembrane isoforms hCA IX and XII over the ubiquitous isoforms hCA I and II. Most of them presented a complete loss of hCA II inhibition (K(i)s > 10,000 nM) and strong inhibitory activity against hCA IX and XII in the nanomolar range with respect to the parent compound. A residual activity against hCA I was observed for some of them. These biological results have been explained by docking studies within the active sites of the four studied human carbonic anhydrases (with or without the zinc-bound water) and helped us to better comprehend the rationale behind the design of tertiary sulfonamide compounds as potent but atypical inhibitors of specific isoforms of human carbonic anhydrase.

Design, Synthesis and Biological Evaluation of Two Opioid Agonist and Cav2.2 Blocker Multitarget Ligands

N‐type voltage‐dependent Ca2+ channels (CaV2.2) are located at nerve endings in the central and peripheral nervous systems and are strongly associated with the pathological processes of cerebral ischaemia and neuropathic pain. CaV2.2 blockers such as the ω‐conotoxin MVIIA (Prialt) are analgesic and have opioid‐sparing effects. With the aim to develop new multitarget analgesic compounds, we designed the first ω‐conotoxin/opioid peptidomimetics based on the enkephalin‐like sequence Tyr‐D‐Ala‐Gly‐Phe (for the opioid portion) and two fragments derived from the loop‐2 pharmacophore of ω‐conotoxin MVIIA. Antinociceptive activity evaluated in vitro and in vivo revealed differential affinity for CaV2.2 and opioid receptors and no significant synergistic activity.

Antinociceptive profile of potent opioid peptide AM94, a fluorinated analogue of biphalin with non-hydrazine linker†

AM94 is a fluorinated analog of biphalin with non‐hydrazine linker that has an in vitro affinity for μ‐opioid and δ‐opioid receptors tenfold higher than biphalin. Furthermore, in vivo evaluation in rats showed that AM94 has in hot plate test – after both intracerebroventricular and intravenous administrations – a greater and more durable efficacy than biphalin. Here, the antinociceptive profile of AM94 is further evaluated by following two different administration routes, intrathecal and subcutaneous, and two different animal species, rats and mice. The analgesic potency of AM94 is compared with that of both the parent peptide biphalin and morphine. Results show that in rats (tail flick test) and in mice (formalin test), AM94 has a higher and more durable analgesic effect than biphalin after intrathecal and subcutaneous administrations. Conformational properties of biphalin and AM94 were also investigated by variable‐temperature 1H NMR and energy minimization. Copyright

Hybrid peptides endomorphin-2/DAMGO: Design, synthesis and biological evaluation

Endomorphin-2 [Tyr-Pro-Phe-Phe-NH2] and DAMGO [Tyr-D-Ala-Gly-(N-Me)Phe-Gly-ol] are natural (EM2) and synthetic (DAMGO) opioid peptides both selective for μ opioid receptor with high analgesic activity. In this work we report synthesis, in vitro and in vivo biological evaluation of five new hybrid EM2/DAMGO analogues, with the aim to obtain compounds with high affinity at μ-opioid receptor, high activity in animal nociception tests (hot plate and tail flick) and improved enzymatic stability. Double N-methylation on both Phe residues and C-terminal ethanolamide led to analogue 6e, which possesses a good in vitro μ affinity (Kiμ=34 nM), combined with a remarkable in vivo antinociceptive activity.

Role of Formyl Peptide Receptors (FPR) in Abnormal Inflammation Responses Involved in Neurodegenerative Diseases

Neurodegenerative disorders, such as multiple sclerosis, prion diseases, Alzheimers disease and Parkinsons disease are often associated with inflammatory process, which involves various components of the immune system in the central nervous system, in particular astrocytes and microglial cells. Inflammation mediators such as cytokines, leukotrienes, superoxide radicals, eicosanoids, the complement cascade, and FPR agonists (formyl peptides) may play a significant role in pro-inflammatory responses, in which infiltration of activated mononuclear phagocytes at the sites of lesion is a common feature. To prevent long-term inflammation damage, the central nervous system could be treated with antinflammatory agents such as non-steroidal anti-inflammatory drugs (NSAIDs), but only few drugs were found to be effective and their therapeutic benefits is limited by side effects. Accumulating evidences suggest that targeting glia-neuron system might be a therapeutic approach in the treatment of neurodegenerative disease progression, in particular of Alzheimers disease. Aminopyridazine derivative discovered in unbiased cell-based screens for new synthetic compounds, have proved to be able to suppress selective glial activation responses via mechanisms distinct from NSAIDs. In this review, we report the potential involvement of FPR receptors in inflammatory responses and the potential use of their antagonists to modulate the inflammatory responses of the microglia. Recent results demonstrate that targeting of inflammatory glia cytokine pathways, can suppress Aβ-induced neuroinflammation in vivo, resulting in the attenuation of neuronal damage.

Exploring the biological consequences of conformational changes in aspartame models containing constrained analogues of phenylalanine

Abstract The dipeptide aspartame (Asp-Phe-OMe) is a sweetener widely used in replacement of sucrose by food industry. 2′,6′-Dimethyltyrosine (DMT) and 2′,6′-dimethylphenylalanine (DMP) are two synthetic phenylalanine-constrained analogues, with a limited freedom in χ-space due to the presence of methyl groups in position 2′,6′ of the aromatic ring. These residues have shown to increase the activity of opioid peptides, such as endomorphins improving the binding to the opioid receptors. In this work, DMT and DMP have been synthesized following a diketopiperazine-mediated route and the corresponding aspartame derivatives (Asp-DMT-OMe and Asp-DMP-OMe) have been evaluated in vivo and in silico for their activity as synthetic sweeteners.

DPP-4 inhibitors: a patent review (2012 – 2014)

Introduction: Dipeptidyl peptidase 4 (DPP-4) is a serine protease, which catalyzes the hydrolytic process of the amide bond X-Ala or X-Pro at the N-terminus of peptides. This enzyme is involved in the degradation of two incretin hormones glucagon-like peptide-1 and glucose-dependent-insulinotropic polypeptide, which increase the production and release of insulin. Therefore, DPP-4 inhibitors are considered as one of the well-established therapies available for type 2 diabetes mellitus. Areas covered: In this review, the authors report all the patents related to DPP-4 inhibitors from 2012 to 2014. The chemical-related patents have been divided in three general families: i) peptidomimetics; ii) peptides; and iii) non-peptidomimetics compounds. The third group is the most consistent; thus the patents have been further divided on the basis of the chemical structure. In the last section, we briefly discuss the patents containing the formulations or associations of DPP-4 inhibitors with other drugs. Expert opinion: In the last few years, the research on DPP-4 inhibitors has significantly grown leading to the development of heterocyclic scaffolds and non-peptidomimetic structures. Unfortunately, these compounds are not immune from side effects associated with the inhibition of other substrates, indicating that DPP-4 inhibitors are likely multi-target drugs. Therefore, their potential multi-target effects require more attention in clinical practice, even if at this moment, all the patents are focused only on diabetes.

Synthesis and anti-cancer activity of naturally occurring 2,5-diketopiperazines

Three naturally occurring oxyprenylated diketopiperazines were synthesized and preliminarily tested as growth inhibitory agents in vitro against various cancer cell lines. The compounds were tested on six human cancer cell lines with different sensitivity to proapoptotic stimuli using the MTT colorimetric assay. The data revealed that of the chemicals under study only deoxymicelianamide (11) displayed the highest activity, recording mean IC50 growth inhibitory values ranging from 2 to 23 μM. A comparative study with the non-geranylated saturated derivative of (11) revealed the importance of the presence of the geranyloxy side chain and the exocyclic 2,5-DPK double bond moiety for the observed activity.

Potent Biphalin Analogs with µ/δ Mixed Opioid Activity: In Vivo and In Vitro Biological Evaluation

Biphalin [(Tyr‐D‐Ala‐Gly‐Phe‐NH‐)2] is an octapeptide with mixed μ/δ opioid activity. Its structure is based on two identical enkephalin‐like portions linked “tail‐to‐tail” by a hydrazine bridge. This study presents the synthesis and in vitro and in vivo bioassays of two biphalin analogs that do not present the toxicity connected with the presence of the hydrazine moiety and are able to elicit a higher antinociceptive effect than biphalin.