Preclinical

The approval of a new drug requires preclinical and chnical studies and takes an average of 10 years to complete. The preclinical and chnical trials have to prove the safety and efficacy of every new medicine. 

The preclinical trials are performed in in vitro and animal studies to assess the biological activity of the new compound. In phase 1 of the clinical trials the safety of a new drug is examined and the dosage is determined by administering the compound to about 20 to 100 healthy volunteers. The focus in phase II is directed onto the issues of safety, evaluation of efficacy, and investigation of side effects in 100 to 300 patient volimteers. More than 1000 patient volunteers are treated with the new drug in phase 111 to prove its efficacy and safety over long-term use. 

A newel class of hypnotic at the pieclinical stage as of this writing (ca 1993) are the neuiosteioids, also known as the epalons and represented by (30) (9), interact with the GABA /BZ receptor complex, have shown interesting activity in preclinical models (10), and are... 

Newel experimental approaches to anxiety therapy include ligands interacting with the ligand-gated ion channels that are selectively activated by nicotine, C qH 4N2 (87), the well-known active ingredient of cigarettes which has anxiolytic actions (42). Cholecystokinin B receptor ligands, specifically the dipeptoid, CI-988 [130404-91 -0] 02 1142 40 (88) have demonstrated anxiolytic activity ia preclinical models (43). 

A new generation of antiinflammatory agents having immunosuppressive activity has been developed. The appearance of preclinical and clinical reports suggest that these are near entry to the pharmaceutical market. For example, tenidap (CP-66,248) (12) has been demonstrated to inhibit IL-1 production from human peripheral blood monocytes in culture (55). Clinically, IL-1 in synovial fluids of arthritic patients was reduced following treatment with tenidap. Patients with rheumatoid or osteoarthritis, when treated with tenidap, showed clinical improvement (57,58). In addition to its immunological effects, tenidap also has an antiinflammatory profile similar to the classical NSAIDs (59). Other synthetic inhibitors of IL-1 production are SKF 86002 (20) andE-5110 (21) (55). 

Immunosuppression induced by sirolimus (36) appears to be mediated by a mechanism distincdy different from that of either cyclosporin or FK-506. Sirolimus markedly suppresses IL-2 or IL-4-driven T-ceU proliferation. The preclinical studies suggest that sirolimus is a potent immunosuppressive agent in transplantation and autoimmune disease models. The clinical potential of this agent depends on its toxicity profile (80). 

The mechanism of action of nootropic agents has been proposed to be their abiUty to faciUtate information acquisition, consoHdation, and retrieval (36). No one particular effect has been observed with any consistency for these agents, thus whereas a considerable amount of diverse preclinical pharmacological behavioral data has been generated using these compounds, the significance of these results in predicting clinical efficacy has not been established (43,44). Reviews on the biochemical and behavioral effects of nootropics are available (45—47). 

There is increasing pressure to develop homochiral dmgs (34). Growing demands are faced by the pharmaceutical industry in dmg development to consider chiral issues in the eady preclinical phases of dmg design and synthesis. 

Numerous neuropeptides are beheved to be involved with the transmission or inhibition of pain, and the hope is to utilize this approach as a strategy to induce analgesia. Substance P is reported to be a transmitter of nociceptive impulses (39), and therefore antagonists should be analgesic. Capsaicin [404-86-4], C2gH2yN02, is known to deplete substance P and cause analgesia (40), but its side effects are intolerable. Antagonists to bradykinin [58-82-2], a substance known to induce pain (41), have shown some success in preclinical trials. 

Class III Premarket Approval. Similar to a new dmg approval, a premarket approval grants the appHcant a Hcense to market a specific weU-characterized device. These devices are subject to the requirements of Section 515 of the Eood, Dmg, and Cosmetic Act. A post-amendment device is a device put ia commercial distribution after May 28, 1976. If it is not substantially equivalent to a preamendment device it is automatically ia Class 111, and a premarket approval appHcation (PMA) is required. The appHcation must iaclude reports of preclinical and clinical studies done ia support of claims of safety and efficacy as well as any labeling claims made for the device. Once the PMA is submitted, the PDA determines whether the appHcation iacludes the required information. If the PMA is suitable for scientific review, the PDA has 180 days from the filing date to approve or deny the appHcation. Polybutester, polydioxanone, polyglyconate, and ePTPE sutures are all regulated as Class 111 devices. 

Year is year of launch in the U.S. market unless indicated Pre-Cl = preclinical, Ph III = phase III clinical trials (status as of Feb. 1990). 

The stmctures of selected cephalosporins on the U.S. market, or in the final stages of development, are shown in Tables 4—8 (see also 78, 87). For every cephalosporin which has made it to the marketplace, HteraHy thousands of analogues were synthesized in order to estabUsh the stmcture-activity profile and allow selection of a clinical candidate. In addition to these compounds, there is a tremendous number of cephalosporin compounds currendy at various stages of development. A more extensive listing of the newer cephalosporins under preclinical or clinical evaluation may be found in a number of reviews (79,88). 

Another successhil strategy for derivatization of erythromycin employed modification of functional groups involved in intramolecular cyclizations. The C-9 ketone, C-6 hydroxyl group, C-8 proton, and/or C-ll,12-diol of erythromycin were converted into functional groups which participate poorly, if at all, in intramolecular cyclizations. Some derivatives which have been extensively evaluated in preclinical and clinical trials exhibit such desirable properties as better stabiUty under acidic conditions, greater oral bioavadabihty, and higher and more prolonged concentrations of antibiotic in semm and tissues. 

Japan. In Japan, registration of dmgs for aquatic species requires the same data as those required for dmgs on other animals. The Ministry of Agriculture, Eorests, and Eisheries and the Ministry of Welfare control the use of chemicals in aquaculture in Japan (17). The preclinical data requirements include product chemistry, toxicity (acute, subacute, special) using rats and mice, safety to target animals, and metaboHsm. The requirements for clinical data include avadabiHty and residues. As of July 1990, more chemicals were registered for aquacultural use in Japan than in any other country (Table 4). 

Toxicity Amelioration. Cancer researchers traditionally have not focused their attention on the question of toxicity amehoration. This is partiy attributed to the lack of predictive animal models for human toxicities. For example, the preclinical rat model, used as a predictor of myelosuppression, has failed to predict myelosuppression in humans in clinical trials. In addition, reduction of one toxicity may result in the emergence of another, more serious problem. Research efforts to address the problem of toxicity amelioration has progressed in several directions. The three most prominent areas are analogue synthesis, chemoprotection, and dmg targeting. 

Two new female condoms, ie, vaginal pouches, are in early stages of development. These devices still require thorough preclinical and clinical studies to demonstrate safety and effectiveness before they reach the market (102). 

Figure 11 Antiinflammatory or anti-cancer marine natural products and synthetic analogs that are in commercial use or in clinical and preclinical evaluation...

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