Antimalarial N,N′-substituted biguanides derived from...

Details Antimalarial N,N′-substituted biguanides derived from... Antimalarial N,N′-substituted biguanides derived from...

2001-03-14

2003-04-22

Page, Thurman K. (Department: 1615)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Capsules

C424S400000, C424S464000, C424S422000, C514S633000, C514S331000, C514S616000, C514S660000

Reexamination Certificate

active

06551614

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to N,N′-substituted asymmetrical imidodicarbonimidic diamides derived from hydroxylamines and their derivatives, to a process for making them, to a pharmaceutical composition thereof and a method for protecting and/or treating a mammalian subject from infections caused by an organism selected from the group consisting of Plasmodium sp., Mycobacterium sp. and
Pneumocystis carinii.
2. Reported Developments
Malaria is an infectious febrile disease caused by protozoa of the genus Plasmodium, which are parasitic in the red blood cells, and are transmitted by the bites of infected mosquitoes of the genus Anopheles. The disease is characterized by attacks of chills, fever, and sweating, occurring at intervals which depend on the time required for development of a new generation of parasites in the body. After recovery from the acute attack, the disease has a tendency to become chronic, with occasional relapses. Among the various forms of malaria falciparum or pernicious malaria is the most serious form of malaria caused by
Plasmodium falciparum
, characterized by severe constitutional symptoms and sometimes causing death. The disease is prevalent in tropical and subtropical areas of the world including the Amazon region of Brazil, East and Southern Africa and Southeast Asia. Malaria has been treated with various drugs throughout recent history including combinations of drugs. While marginally successful against some strains of malaria, most strains of malaria appear to have developed resistance not only to individual drugs but also to multiple combinations of drugs. Multiple Drug Resistance, hereinafter sometimes referred to as MDR, continues to confound antimalarial drug development efforts. Drugs of diverse chemical classes, such as mefloquine, halofantrine, and artemisinin, appear to be expelled by a common transport or efflux mechanism. The mechanism of resistance to the classic antifolate antimalarials is independent of drug transport or efflux and is due to differential binding affinities to parasite dihydrofolate reductase, hereinafter sometimes referred to as DHFR, and or dihyropteroate synthase, hereafter sometimes referred to as DHPS. Efforts have been and are being made to develop DHFR inhibitors in combination with DHPS inhibitors. The efforts so far have resulted in limited success.
U.S. Pat. No. 5,322,858 to Canfield et al., which is incorporated herein by reference in its entirety, discloses N,N′substituted imidocarbonimidic diamides derived from hydroxylamines, pharmaceutical formulations thereof, and methods of protecting subjects from Plasmodium sp., Mycobacterium sp. and
Pneumocystis carinii
by administering to a subject liable to such infection a prophylactically effective amount of said pharmaceutical formulations. The formulations are said to reduce the level of infection where said subjects have already been infected.
The patent discloses a large number of compounds in generic formula 1:
wherein:
wherein R
1
is a substituted or unsubstituted divalent aliphatic group of 1 to 16 carbon atoms; wherein the substituents are mono or poly and are selected from the group consisting of lower alkyl, aryl and arlkyl, R
3
is selected from the group consisting of the same group of values as R
5
other than carbocycloaryl, and when further bonded to the nitrogen to which it is attached, a saturated heterocycle of 4-8 carbon atoms, R
5
is selected from the group consisting of substituted and unsubstituted alkyl of 1-10 carbon atoms, aryl, cycloalkyl and heterocycloalkyl of 3-8 carbon atoms, mono or polycarbocycloaryl of 4-7 atoms per ring, wherein the substituents are; mono or poly and are selected from the group consisting of lower alkyl, cycloalkyl of 3-8 carbon atoms, lower alkenyl, lower alkynyl, nitro, lower alkoxy, lower alkoxycarbonyl, phenyl loweralkyl, phenyl, mono and polyhalophenyl, phenoxy, mono and polyhalophenoxy, and halo provided however, that such halo substitution is in a mono and polycarbocycloaryl of 4-7 atoms per ring. R
6
and R
7
which may be the same or different are hydrogen alkanoyl or alkoxy alkanoyl, and when further bonded to the nitrogen to which either is attached, a saturated heterocycle of 4-8 carbon atoms, and R
7
may also be selected from the group consisting of same group of values as R
5
, and when further bonded to the nitrogen to which it is attached, a saturated or unsaturated heterocycle of 4-8 carbon atoms, Y is oxygen or sulfur, q is 0 or 1, n m is 1 or 0, having the latter value where R
3
is a moiety having two bonds attached to N
5
, provided that unless otherwise stated the prefix alk designates moieties which are straight chain or branched chain of 1-24 carbon atoms, and when further prefixed by the term lower, designates 1-6 carbon atoms, the respective tautomers thereof, the pharmaceutically acceptable salts and addition salts thereof and the hydrates of said salts and addition salts and mono and diacyl derivatives thereof.
In testing the compounds disclosed in the patent for antimalarial activity, one candidate, identified as WR250417 or PS15, hereinafter sometimes referred to as PS15, was demonstrated to have significant activity against drug-resistant
Plasmodium falciparum
as described by Canfield et al. 1993. PS-15: A potent, orally active antimalarial from a new class of folic acid antagonists. Am J. Trop Med Hyg 49: 121-126. The compound, N[3-(2,4,5-trichlorophenoxy)propyloxy]-N′-(1-methylethyl)imidodicarbonimidediamide hydrochloride has the structure:
The compound was found to be not cross-resistant with other inhibitors of DHFR, such as pyrimethamine and cycloguanil.
While PS-15 is similar in chemical structure to the well-known antimalarial drug Proguanil,
it was envisioned to present a new series of antifolate drugs which were named hydroxylamine-derived biguanides. PS-15 displayed modest intrinsic antimalarial activity alone and was metabolized in vivo to WR99210, the extremely active triazine inhibitor of DHFR having the chemical structure
When tested in vitro against drug-resistant clones of
P. falciparum
, it was found to be more active than proguanil, and the putative metabolite WR99210, and was found to be ten thousand times more active than the proquanil metabolite cycloguanil. PS-15 is also more active as well as less toxic than proguanil when administered orally to mice infected with
P. berghei
. When administered orally to Aotus monkeys infected with multidrug-resistant
P. falciparum
, the drug is more active than either proquanil or WR99210. Because PS15 had intrinsic antimalarial activity, and is not cross-resistant with other DHFR inhibitors, and could be metabolized to WR99210 in vivo, oral administration of this drug was predicted to circumvent the shortcomings and retain advantages found with both proguanil and WR99210. However, development of PS-15 was stifled by environmental regulatory compliance issues which prohibited the use of required starting material, 2,4,5-trichlorophenol in bulk drug manufacturing. The synthesis of PS-15 is shown in EXAMPLE 1, U.S. Pat. No. 5,322,858.
Numerous analogs of PS-15 were prepared and several were found to have equivalent antimalarial activity. A 90-day comparative toxicity experiment showed that, with the exception of PS-26 and PS-33, PS-15 and its analogs caused testicular toxicity.
SUMMARY OF THE INVENTION
We have now synthesized a series of N,N′-substituted biguanides and, unexpectedly, two of this series of N,N′-subsitituted biguanides were found to be free of testicular atrophy found with the other compounds in the series. The compounds are: 1-[3-(3,4-dichlorophenoxy)propyloxy]-5-isopropylbiguanide(hemisuccinate), hereinafter sometimes designated as PS-26
1-[3-(4-chlorophenoxy)propyloxy]-5-isopropylbiguanide(hemisuccinate), hereinafter sometimes designated as PS-33
The compounds of the present invention are formulated with a pharmaceutically acceptable carrier for oral or injectable administration.
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