Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Having -c- – wherein x is chalcogen – bonded directly to...
Reexamination Certificate
2000-02-22
2001-06-05
Lee, Howard C. (Department: 1623)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Having -c-, wherein x is chalcogen, bonded directly to...
C514S280000, C546S048000
Reexamination Certificate
active
06242457
ABSTRACT:
The present invention relates to compounds having antitumor activity, in particular to new derivatives of camptothecins, processes for their preparation, their use as antitumor drugs and pharmaceutical compositions containing them as active ingredients.
BACKGROUND OF THE INVENTION
Camptothecin is an alkaloid, which was isolated by Wall et al (J. Am. Chem. Soc. 88, 3888-3890 (1966)) for the first time from the tree Camptoteca acuminata, a plant originating from China, of the Nyssaceae family.
The molecule consists of a pentacyclic structure having a lactone in the ring E, which is essential for cytotoxicity.
The drug demonstrated a wide spectrum of antitumor activity, in particular against colon tumors, other solid tumors and leukemias, and the first clinical trials were performed in the early 70's. Since Camptothecin (in the following briefly CPT) has low water solubility and in order to prepare clinical trials, the National Cancer Institute (NCI) prepared the sodium salt (NSC100880), which is water-soluble. Clinical trials in phase I and II, were not completed because of the high toxicity showed by the compound (hemorrhagic cystitis, gastrointestinal toxicity, such as nausea, vomit, diarrhoea, and myelosuppression, especially leucopenia and thrombocytopenia.
In any case, sodium salt showed a lower activity than CPT, because, at pH 7.4, the inactive form (open ring) predominates on the lactone-active one (closed ring), which predominates at pH<4.0.
Subsequently, many CPT analogues were synthesised in order to obtain compounds with lower toxicity and higher water solubility. Two drugs are marketed, Irinotecan (CPT-11), marketed with the Trade Mark Camptosar® by Upjohn and Topotecan, marketed with the Trade Mark Hymcamptamin® or Thycantin®, by Smith Kline & Beecham. Other derivatives are in different steps of clinical development in phase II, such as NSC-603071 (9-aminocamptothecin), 9-NC or 9-nitrocamptothecin, an oral prodrug converted in 9-aminocamptothecin, GG-211 (GI 147211), and DX-8591f, the latter being water-soluble. All the derivatives identified to date contain the parent structure with 5 rings, essential for cytotoxicity. It was demonstrated that modifications on the first ring, such as in the case of the above-mentioned drugs increase water solubility and allow a higher tolerability of the drug.
Water-soluble Irinotecan was approved for the treatment of many solid tumors and ascites (colon-rectum, skin, stomach, breast, small and non-small cell lung, cervix and ovarian cancer and in non-Hodgkin lymphoma). Moreover, Irinotecan resulted active in solid tumors resistant to Topotecan, vincristine or melphalan and MDR-1 cells resulted marginally resistant to the drug. The active metabolite was identified as the 10-hydroxyderivatives (SN-38), produced by the action of carboxylesterases. CPT-11 showed a good activity using different administration routes, such as intraperitoneal, intravenous, oral (Costin D., Potmhexyl M. Advances in Pharmacol. 29B, 51-72 1994).
CPT-11 was administered also with cisplatin or etoposide, showing a synergistic effect, thanks to the ability to hinder DNA repair. Also in this case, however, a grade 3 and 4 leucopenia and diarrhoea arose (Sinha B. K. (1995) Topoisomerase inhibitors. Drugs 49, 11-19, 1995).
Topotecan has a significant oral bioavailability. Oral administration proved to be convenient to reach a prolonged exposition to the drug, without the use of temporary catheters being necessary (Rothenberg M. L. Annals of Oncology 8, 837-855, 1997). Also this water-soluble CPT analogue showed activity against different types of tumors, with different administration routes, intraperitoneal, intravenous, subcutaneous, oral. The more promising results were obtained with Topotecan hydrochloride, intravenous infusion for 5 days, in different tumors such as small and non-small cell lung, ovarian, breast, stomach, liver, prostatae, soft tissue sarcoma, head and neck, oesophagus, resistant colon-rectum, multiform glioblastoma, chronic and acute myelocytic leukemias. However, also in this case, severe side effects occurred, such as neutropenia and thrombocytopenia, whereas gastrointestinal toxicity, such as nausea, vomit and diarrhoea were milder.
It was demonstrated that the main transformation and elimination pathways of the drug comprise lactone hydrolysis and urinary excretion: in fact, lactone form is 50% hydrolysed to open ring, 30 min after infusion. Topotecan crosses hematoencephalic barrier 10 min after infusion (30% in the cerebrospinal fluid with respect to plasma). On the contrary, camptothecin does not cross hematoencephalic barrier in significant amount, probably due to its binding with proteins.
Clinical development of 9-aminocamptothecin was hampered by its scarce water solubility. Recently, a colloidal dispersion was prepared, which made possible its entry in phase II clinical trial. Prolonged exposition (from 72 hours to 21 days) appeared to be essential to demonstrate antitumor activity, because of its short half-life (Dahut et al., 1994). Responses in patients suffering from not treated colon-rectum, and breast cancer and resistant lymphoma, were noticed. The activity demonstrated against Pgp-positive tumors suggested a lack of cross-resistance against resistant MDR-1 cells. Once again, bone marrow and gastrointestinal toxicity was observed.
Lurtotecan is the most water-soluble analogue, with an activity comparable to Topotecan in vitro. Two regimens were adopted: one 30-min infusion a day for 5 days every 3 weeks and one 72-hours infusion one time every 3 weeks. Responses in patients suffering from, neck, ovarian, breast, liver tumour were observed. Also in this case, hematic toxicity was detected. The molecule is the following:
9-Nitrocamptothecin is an oral prodrug rapidly converted into 9-aminocamptothecin after administration. Responses were observed in patients suffering from pancreas, ovarian, and breast cancer.
Notwithstanding the major part of tumour cells is highly sensitive to topoisomerase I inhibitors, due to the high enzyme levels, some tumoral lines result to be resistant. This is due to other mechanisms, rather than the overexpression of MDR1 and MRP (multidrug resistance associated protein) genes and of their products, P (Pgp) glycoprotein and MRP protein, respectively, for which Topotecan or CPT-11 are not very good substrates, (Kawato Yet al J. Pharm. Pharmacol. 45, 444-448, (1993)).
In fact, it was observed that some resistant tumour cells contain mutant forms of topo I, accordingly the formation of the topo I-DNA complex is damaged or some cells lack in the carboxylesterase activity, necessary for converting CPT-11 in the active metabolite SN-38 and are thus resistant against this drug (Rothenberg, 1997, ibid.).
Within the drugs used in tumour therapy, the interest in inhibitors of topoisomerase I enzymes is attributed to the following considerations: a) efficacy against tumors naturally resistant to conventional drugs, topoisomerase II inhibitors included; b) the levels of the topo I enzyme remain elevated in all phases of the cycle; c) many tumors express high levels of the target enzyme; d) lack of recognition by the proteins involved in the phenomenon of multi-drug resistance (Pgp or MRP) and absence of the detoxifying enzyme-mediated metabolism, associated to the glutathione-dependent system (glutathione peroxidase and glutathione S-transferase) (Gerrits C J H., et al., Brit. J. Cancer 76, 952-962).
Once potential clinical advantages of topoisomerase I inhibitors are taken into consideration, both in terms of antitumor activity, assayed on a wide range of tumors, and the poor induction of pharmaco-resistance, the present research aims to identify topo I inhibitors with a lower toxicity with respect to the one demonstrated by the drugs on the market or in clinical phase. The factors determining the relative potency of camptothecin analogues include a) intrinsic activity of topoisomerase I inhibition; b) drug mean life; c) interaction with plasma proteins; d) the ratio between the circulating active
Carminati Paolo
Merlini Lucio
Penco Sergio
Zunino Franco
Lee Howard C.
Maier Leigh C.
Nixon & Vanderhye
Sigma-Tau Industrie Farmaceutiche Riunite S.p.A.
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