This chapter discusses the available information on ibopamine, rather than being as comprehensively reviewed as the other prodrugs. The usefulness of the prodrug approach to the purpose of improving the delivery and the effectiveness of drugs at their sites of action has been experimentally investigated and widely debated; interesting concepts have been developed and explored at the biopharmaceutic, pharmacokinetic, and pharmacodynamic levels; notwithstanding a large amount of work, many of these concepts do not appear to have general application, and a case-by-case investigation of the optimal requirements remains mandatory. Broad clinical experience provides evidence that ibopamine, the first orally active dopaminergic prodrug investigated and approved for cardiovascular therapy, affords sustained benefit in the chronic treatment of congestive heart failure (CHF) by combined vasodilating and positive inotropic properties; ibopamine appears to offer a new, safe and effective therapeutic approach, either as a sole therapy in mild CHF or in combination with traditional therapy and/or other vasodilators in severe CHF.

The pharmacological activity of 2NTX-99 ([4-methoxy-N1-(4-trans-nitrooxycyclohexyl)-N3-(3-pyridinylmethyl)-1,3-benzenedicarboxamide]) was investigated in vitro in the intact, rat pulmonary vasculature and in guinea pig airways. Rat lungs were perfused at constant flow and changes in vascular tone recorded. Challenge with the TXA₂ analogue 9,11-dideoxy-9α11α-methanoepoxy ProstaglandinF₂ (U46619, 0.5 μM) increased vessel tone (32.48±1.5 vs 13.13±0.56 mmHg; n=12). 2NTX-99 (0.1-100 μM; n=5), caused a concentration-dependent relaxation, prevented by 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, 10 μM, n=4), an inhibitor of soluble guanylate cyclase. Acetylcholine (0.1-10 μM; n=3) and a reference NO-donor, isosorbide-5-mononitrate (5-100 μM; n=4), were ineffective. Intraluminal perfusion of washed human platelets (2 × 10⁸ cells/ml) increased intravascular pressure after challenge with arachidonic acid (AA, 2 μM; n=5), an increase abolished by acetylsalicylic acid and significantly reduced by 2NTX-99 (40 μM; n=5). TXB₂ in the lung perfusate was detected after platelet activation, 2NTX-99 inhibited TXA₂ synthesis (6.45±0.6 and 1.10±0.2 ng/ml, respectively). 2NTX-99 did not alter central or peripheral airway responsiveness to Histamine (0.001-300 μM; n=6), U46619 (0.001-3 μM, n=3) or LTD₄ (1 pM-1 μM; n=6). 2NTX-99 vasodilates the pulmonary vasculature via the release of nitric oxide (NO) and reduces intraluminal, AA-induced, TXA₂ formation. The combined activity of 2NTX-99 as an NO-donor and a TXA₂-synthesis inhibitor provides strong support for its potential therapeutic use in pathologies of the pulmonary vascular bed (e.g. pulmonary hypertension).

In recent years progress has been speeding in studies of cell-cell interaction governed by adhesion molecules, and in particular by integrins and their ligands in cells and in the extracellular matrix. Integrins are distributed in a variety of tissues and blood cells. An increased expression of integrins and of their adhesion counterparts is often observed in sites relevant to disease states. Important roles are played by integrin α(v)β(3) in cancer angiogenesis and metastatic diffusion, in angiogenesis in ischemic tissues, in atherosclerotic damage and restenosis, and in osteoporosis; by integrin α(5)β(1) in angiogenesis processes; by integrin α(II)bβ(3), mediating adhesion of platelets to fibrinogen, in thrombotic conditions; by integrins α(4)β(1) and α(L)β(2) in inflammatory conditions, particularly autoimmune diseases and asthma. Therefore, medicinal chemists became attracted and engaged in research on integrins as therapeutic and diagnostic targets. Many efforts have been directed towards the development of molecular constructs including integrin ligands that can provide advanced tools for drug delivery, for imaging, or for their combination (theranostics), particularly by exploiting the new possibilities offered by nanoparticles. Here we will review the current status and the future perspective of integrin targeting of several kind of nanoparticles, going from most studied micelles, liposomes, polymeric nanoparticles to finish with inorganic nanoparticles of more recent employment. Perfluoroalkane filled microbubbles, although over the nanometric size (1-10 μm) will be shortly considered.

Thromboxane (TX) A(2), prostacyclin (PGI(2)), and nitric oxide (NO) regulate platelet function and interaction with the vessel wall. Inhibition of TXA(2), implemented synthesis of PGI(2), and supply of exogenous NO may afford therapeutic benefit. 2NTX-99 [4-methoxy-N(1)-(4-trans-nitrooxycyclohexyl)-N(3)-(3-pyridinylmethyl)-1,3-benzenedicarboxamide], a new chemical entity related to picotamide, showed antithromboxane activity and NO donor properties. 2NTX-99 relaxed rabbit aortic rings precontracted with norepinephrine or U46619 (9,11-dideoxy-9alpha,11alpha-methanoepoxy-prosta-5Z,13E-dien-1-oic acid; EC(50), 7.9 and 17.1 microM, respectively), an effect abolished by 10 microM 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ). 2NTX-99 inhibited arachidonic acid (AA)-induced washed platelet aggregation (EC(50), 9.8 microM) and TXB(2) formation (-71% at 10 microM), and its potency increased in the presence of aortic rings (EC(50), 1.4 microM). In whole rabbit aorta incubated with homologous platelets, AA caused contraction and TXA(2) formation, reduced by 2NTX-99 (10-40 microM): contraction, -28 and -47%, TXA(2) formation, -37 and -75.4%, respectively, with concomitant increase in PGI(2). 2NTX-99 (20-40 microM) inhibited U46619-induced aggregation in rabbit platelet-rich plasma (PRP) (-74 +/- 6.7 and -96 +/- 2.4%, respectively) and inhibited collagen-induced aggregation in human PRP (-48.2 +/- 10 and -79.2 +/- 6%), whereas ozagrel was ineffective. In human embryonic kidney 293 cells transfected with the TXA(2) receptor isophorm alpha receptor, 2NTX-99 did not compete with the ligand, [(3)H]SQ29,548 ([(3)H][1S-[1alpha,2beta(5Z),3beta,4alpha]]-7-[3-[[2-(phenylamino)-carbonyl]hydrazino]methyl]-7-oxabicyclo[2,2,1]-hept-2-yl]-5-heptanoic acid), or prevent inositol phosphate accumulation. After oral administration (50-250 mg/kg), 2NTX-99 inhibited TXA(2) production in rat clotting blood (-71 and -91%); at 250 mg/kg, an area under the curve, 0 to 16 h, of 149.5 h/microg/ml and a t(1/2) of 6 h were calculated, with a C(max) value of 31.8 +/- 8.2 microg/ml. An excellent correlation between plasma concentrations and TXA(2) inhibition occurs. 2NTX-99 controls platelet function and vessel wall interaction by multifactorial mechanisms and possesses therapeutic potential.

We evaluated the capacity of anti-aggregating agents to influence thromboxane A2 and prostacyclin formation, arachidonic acid-endoperoxide redirection, platelet aggregation and vessel tone, in isolated rabbit aorta incubated with homologous platelets. Picotamide (N,N′bis(3-pyridinylmethyl)-4-methoxy-isophthalamide), the only dual thromboxane A2-synthase inhibitor/receptor antagonist in clinical use, inhibited arachidonic acid-induced platelet aggregation with low potency, increased 180-fold by aorta presence. It inhibited thromboxane A2 formation in platelets and, in aorta presence, increased prostacyclin formation. Ozagrel (OKY-046, (E)-3-(4-(1-imidazolylmethyl)phenyl)-2-propenoic acid), a pure thromboxane A2-synthase inhibitor, behaved similarly to picotamide, although the aorta caused a higher (600-fold) shift. The potency of the antagonist SQ 29,548 (1S-(1α,2β(5Z),3β,4α))-7-(3((2-((phenylamino)carbonyl)hydrazino)methyl)-7-oxabicyclo(2.2.1)hept-2-yl)-5-heptenoic acid) was unaffected by aorta. In coincubation experiments, arachidonic acid-challenge increased thromboxane A2-dependent vessel tone; picotamide increased prostacyclin and reduced thromboxane A2 formation and vasoconstriction. Ozagrel mimicked picotamide; aspirin (acetylsalicylic acid) reduced aorta contractility, thromboxane A2 and prostacyclin formation. SQ 29,548 reduced vasoconstriction without affecting eicosanoids. We demonstrate the importance of redirection of eicosanoids in the mechanism of action of thromboxane A2 inhibitors/antagonists within platelet–vascular wall interactions. These findings bear relevance in the development of novel anti-thrombotic drugs.

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The D1-like, D2-like, α1 and α2 in vitro activities of 2-aminotetraline congeners are reported. Z1046 was selected and the antihypertensive activity in rat and dog was evaluated both by intravenous and oral routes.

6.7-Dimethoxy-3-cyano-3.4-dihydrocarbostyril (7A61, 1), a 2-quinolinone derivative, showed interesting cardiotonic properties in vitro. It exerted potent positive inotropic effects, without any change in heart rate, in guinea pig atrial preparations, and its effects were not dependent upon inhibition of phosphodiesterases, opening of Na+ channels, or inhibition of adenosine receptors. Notwithstanding its structural relationships with milrinone, vesnarinone, and other quinolinones endowed with cardiotonic activity, it appeared that 7A61 does not share any of the main mechanisms of action involved in the pharmacological activity of these compounds. Other experiments also excluded the involvement of other well known mechanisms of cardiac stimulation, such as adrenergic receptor activation or opening of Ca++ channels, the mode of action of 7A61 remaining unexplained. However, contrary to milrinone, 7A61 did not exert cardiotonic effects in human ventricular muscle preparations, thus discouraging further investigation. Although the lack of effect on human heart could not be predicted from the results obtained in several cardiac preparations commonly used in laboratory investigations, the scarce efficacy of 7A61 in comparison with milrinone in dog and cat papillary muscle and in guinea pig ventricular muscle suggests the utility of the latter preparations in laboratory experiments aimed at selecting new potential cardiotonic agents.

The title compounds were prepared with a route which is characterized by the regioselective preparation of 3 or 4 oxydryl protected dopamine and epinine precursors.

This chapter discusses the perspectives in the design and application of dopamine receptor agonists. The chapter discusses main pharmacological and clinical achievements as well as the essential results of the search of pharmacophores and of tentative receptor models, to provide the basis for understanding “third generation” of dopamine receptor agonists. The era of dopamine receptor pharmacology began around 1960. Heralded by the discovery of the neurotransmitter role of dopamine, it was previously regarded only as a metabolic precursor of noradrenaline. A new avenue of investigation of the interactions of agonistic and antagonistic ligands with receptor models directly derived from the structure of the protein is opened by recent advancements. Thus, progress in indirect modeling, based on steric and electronic properties of the ligands, plays an important role not only in the design of new active compounds, but also in the improvement and the validation of the direct models. In these models, it has been generally accepted that at least one phenolic or equivalent function, such as the indole NH group of the ergolines, acts as a hydrogen bond donor with respect to a site of the receptor. The recent discovery of potent dopamine agonists devoid of such functions suggests that recognition modes other than hydrogen bonding may be involved in the corresponding region of the receptor.

In the search for new positive inotropic agents we have investigated a series of 3-dimethylamino-1,2,3,4-tetrahydroquinolines with various substituents on the nitrogen of the quinoline ring. The N-isobutyryl derivative 20 (S903) was selected as the most interesting compound. Interestingly, while cardiac contractility was increased in vitro, heart rate was unchanged or slightly decreased. The positive inotropic activity was partly dependent on an indirect sympathomimetic effect. The (S) absolute configuration of the (-)enantiomer of S903 was established by correlation with (S)-l-dopa.