Bis(4-O-Polyhexaose-Thio)-Phenyl Ureas and Method of Use

1. Field of Invention

The present invention relates to novel cation salts of bis(4-O-polyhexaose-thio)-phenylurea sulfate derivatives, to their use as modulators of the complement system of warm-blooded animals, to the intermediates thereof and to the process for the preparation of such intermediates and end products.

2. Description of the Prior Art

The term "complement" refers to a complex group of proteins in body fluids that, working together with antibodies or other factors, play an important role as mediators of immune, allergic, immunochemical and/or immunopathological reactions. The reactions in which complement participates take place in blood serum or in other body fluids, and hence are considered to be humoral reactions.

With regard to human blood, there are at present more than 20 proteins in the complement system consisting of the so-called classical and alternative pathways. These complement proteins are generally designated by the letter C and by number: C1, C2, C3 and so on up to C9. The complement protein C1 is actually an assembly of subunits designated C1q, C1r and C1s. The numbers assigned to the complement proteins reflect the sequence in which they become active, with the exception of complement protein C4, which reacts after C1 and before C2. The numerical assignments for the proteins in the complement system were made before the reaction sequence was fully understood. A more detailed discussion of the complement system and its biochemical, biological and pathological role in the body processes can be found in, for example, Bull. W. H. O. 39: 935 (1968); Annu. Rev. Med. 19: 1 (1968); Johns Hopkins Med. J. 128: 57 (1971); Harvey Lect. 66: 75 (1972); N. Engl. J. Med. 287: 452, 489, 545, 592, 642 (1972); Sci. Am. 229 (5): 54 (1973); Fed. Pro. 32: 134 (1973); Med. World, Oct. 11, 1974, p. 53; J. Allergy Clin. Immunol. 53: 298 (1974); Cold Spring Harbor Conf. Cell Proliferation 2/Proteases Biol. Control: 229 (1975); Annu. Rev. Biochem. 44: 697 (1975); Complement in Clinical Medicine, Dis. Mon. (1975); Complement, Scope, December 1975; Ann. Intern. Med. 84: 580 (1976); Transplant Rev.: 32 (1976); "Complement: Mechanisms and Functions," Prentice-Hall, Englewood Cliffs, N.J. (1976); Essays Med. Biochem. 2: 1 (1976); Hosp. Pract. 12: 33 (1977); Perturbation of Complement in Disease, Chap. 15 in Biol. Amplification Systems in Immunol. (Ed. Day and Good), Plenum, New York and London (1977); Am. J. Clin. Pathol. 68: 647 (1977); Biochem. Soc. Trans. 5: 1659 (1977); Harvey Lect. 72: 139 (1976-1977); J. Periodontol. 48: 505 (1977); Biochem. Soc. Trans. 6: 798 (1978); Clin. and Exp. Dermatol. 4: 271 (1979); Infect. Dis. Rev. 1: 483 (1979).

The complement system (e.g., classical pathway) can be considered to consist of three subsystems: (1) a recognition unit (C1q) which enables it to combine with antibody molecles that have detected a foreign invader; (2) an activation unit (C1r, C1s, C2, C4, C3) which prepares a site on the neighboring membrane; and (3) an attack unit (C5, C6, C7, C8 and C9) which creates a "hole" in the membrane. The membrane attack unit is non-specific; it destroys invaders only because it is generated in their neighborhood. In order to minimize damage to the host's own cells, its activity must be limited in time. This limitation is accomplished partly by the spontaneous decay of activated complement and partly by interference by inhibitors and destructive enzymes. The control of complement, however, is not perfect, and there are times when damage is done to host's cells. Immunity is, therefore, a double-edged sword.

Activation of the complement system also accelerates blood clotting. This action comes about by way of the complement-mediated release of a clotting factor from platelets. The biologically active complement fragments and complexes can become involved in reactions that damage the host's cells. These pathogenic reactions can result in the development of immune-complex diseases. For example, in some forms of nephritis, complement damages the basal membrane of the kidney, resulting in the escape of protein from the blood into the urine. The disease disseminated lupus erythematosus belongs in this category; its symptoms include nephritis, visceral lesions and skin eruptions. The treatment of diphtheria or tetanus with the injection of large amounts of antitoxin sometimes results in serum sickness, an immune-complex disease. Rheumatoid arthritis also involves immune complexes. Like disseminated lupus erythematosus, it is an autoimmune disease in which the disease symptoms are caused by pathological effects of the immune system in the host's tissues. In summary, the complement system has been shown to be involved with inflammation, coagulation, fibrinolysis, antibody-antigen reactions and other metabolic processes.

In the presence of antibody-antigen complexes the complement proteins are involved in a series of reactions which may lead to irreversible membrane damage if they occur in the vicinity of biological membranes. Thus, while complement constitutes a part of the body's defense mechanism against infection it also results in inflammation and tissue damage in the immunopathological process. The nature of certain complement proteins, suggestions regarding the mode of complement binding to biological membranes and the manner in which complement effects membrane damage are discussed in Annu. Rev. Biochem. 38: 389 (1969); J. Exp. Med. 141: 724 (1975); J. Immunol. 116: 1431 (1976); 119: 1, 1195, 1358, 1482 (1977); 120: 1841 (1978); Immunochemistry 115: 813 (1978); J. Biol. Chem. 254: 9908 (1979).

A variety of substances have been disclosed as inhibiting the complement system, i.e., as complement inhibitors. For example, the compounds, 3,3'-ureylenebis-[6-(2-amino-8-hydroxy-6-sulfo-1-naphthylazo)benzenesulfon ic acid], tetrasodium salt (chlorazol fast pink), heparin and a sulphated dextran have been reported to have an anticomplementary effect, Br. J. Exp. Pathol. 33: 327 (1952). German Pat. No. 2,254,893 or South African Pat. No. 727,923 discloses certain 1-(diphenylmethyl)-4-(3-phenylallyl)piperazines useful as complement inhibitors. Other chemical compounds having complement inhibiting activity are disclosed in, for example, J. Med. Chem. 12: 415, 902, 1049, 1053 (1969); Can. J. Biochem. 47: 547 (1969); J. Immunol. 104: 279 (1970); J. Immunol. 106: 241 (1971); J. Immunol. 111: 1061 (1973); Biochim. Biophys. Acta 317: 539 (1973); Life Sci. 13: 351 (1973); J. Immunol. 113: 584 (1974); Immunology 26: 819 (1974); J. Med. Chem. 17: 1160 ( 1974); Biochim. Biophys. Res. Comm. 67: 225 (1975); Ann. N.Y. Acad. Sci. 256: 441 (1975); J. Med. Chem. 19: 634, 1079 (1976); J. Immunol. 118: 466 (1977); Arch. Int. Pharmacodyn. 226: 281 (1977); Biochem. Pharmacol. 26: 325 (1977); J. Pharm. Sci. 66: 1367 (1977); Chem. Pharm. Bull. 25: 1202 (1977); Biochim. Biophys. Acta 484: 417 (1977); J. Clin. Microbiol. 5: 278 (1977); Immunochemistry 15: 231 (1978); Immunology 34: 509 (1978); J. Exp. Med. 147: 409 (1978); Thromb. Res. 14: 179 (1979); J. Immunol. 122: 2418 (1979); J. Chem. Soc. Chem. Comm. 726 (1979); Immunology 36: 131 (1979); Biochim. Biophys. Acta 611: 196 (1980); and J. Med. Chem. 23: 240 (1980).

It has been reported that the known complement inhibitors, epsilon-aminocaproic acid and tranexamic acid, have been used with success in the treatment of hereditary angioneurotic edema, a disease state resulting from an inherited deficiency or lack of function of the serum inhibitor of the activated first component of complement (C1 inhibitor), N. Engl. J. Med. 286: 808 (1972); 287: 452 (1972); Ann. Intern. Med. 84: 580 (1976); J. Allergy Clin. Immunol. 60: 38 (1977). Also androgenic steroids have been used successfully in the treatment of this physiological disorder; see Medicine 58: 321 (1979); Arthritis Rheum. 22: 1295 (1979); Am. J. Med. 66: 681 (1979); and J. Allergy Clin. Immunol. 65: 75 (1980).

It has also been reported that the drug pentosan-polysulfoester has an anticomplementary activity on human serum, both in vitro and in vivo, as judged by the reduction in total hemolytic complement activity, Pathol. Biol. 25: 33; 25 (2): 105; 25 (3): 179 (1977).

The instant invention relates to new compounds bis(4-O-polyhexaose-thio)-phenylurea sulfate derivatives and the cation salts thereof, that modulate the complement system, thereby modulating complement activity in body fluids. Moreover, this invention involves a method of modulating the complement system in a body fluid which comprises subjecting body fluid complement to the action of an effective complement modulating amount of the above-identified compounds. This invention further concerns a method of modulating the complement system in a warm-blooded animal which comprises administering to said animal an effective complement modulating amount of the above-identified compounds.

The invention also deals with the novel precursors that act as intermediates in preparing the above-described complement modulating compounds of this invention.

In accordance with the present invention, there are provided novel compounds represented by the following generic Formula I: ##STR1## wherein X is --SO.sub.3 M and M is a nontoxic pharmaceutically acceptable cation salt, wherein the salt forming moiety is selected from the group consisting of alkali metal, alkaline earth metal, aluminum, ammonia and substituted ammonia selected from the group consisting of trialkylamine (C.sub.1 -C.sub.6), piperidine, pyrazine, alkanolamine (C.sub.2 -C.sub.6) and cycloalkylamine (C.sub.3 -C.sub.6).

Particularly preferred compounds of Formula I which are of major interest as modulators of the complement system are tetradecasodium N,N'-bis[4-[[2,3-6-tri-O-sulfo-4-O-(2,3,4,6-tetra-O-sulfo-.alpha.-D-glucop yranosyl)-.beta.-D-glucopyranosyl]thio]phenyl]urea and its corresponding tetradecatriethylammonium derivative.

This invention further deals with a method of modulating the complement system in a body fluid, such as blood serum, which comprises subjecting body fluid complement to the action of an effective complement inhibiting amount of a compound of the above Formula I. Body fluids can include blood, plasma, serum, synovial fluid, cerebrospinal fluid, or pathological accumulations of fluid such as pleural effusion, etc. This invention also concerns a method of inhibiting the complement system in a warm-blooded animal which comprises administering to said warm-blooded animal an effective complement inhibiting amount of a compound of the above Formula I.

In addition, this invention is concerned with the precursors in the preparation of the complement modulating compounds of Formula I, shown by the following Formula II: ##STR2## wherein Y is selected from the group consisting of --H and --COCH.sub.3.

Specific compounds of Formula II which are of particular interest as intermediates for the production of the compounds of Formula I include the following:

N,N'-bis[4-[[2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-.alpha.-D-gluco pyranosyl)-.beta.-D-glucopyranosyl]thio]phenyl]urea

N,N'-bis[4-[(4-O-.alpha.-D-glucopyranosyl-.beta.-D-glucopyranosyl)thio]phen yl]urea

In the above Formulas I and II the sugar molecule is drawn to represent either maltose or cellobiose. This invention is not restricted to these two disaccharides, but instead is intended to include disaccharides consisting of aldohexoses, ketohexoses, aldopentoses and the like as well as oligosaccharides wherein the sugar units are 2-8 consisting of maltotrioses, maltotetraoses, maltopentaoses and the like.

The compounds of Formula I find utility as complement modulators in body fluids and as such may be used to ameliorate or prevent those pathological reactions requiring the function of complement and in the therapeutic treatment of warm-blooded animals having immunologic diseases such as rheumatoid arthritis, systemic lupus erythematosus, certain kinds of glomerulonephritis, certain kinds of autoallergic hemolytic anemia, certain kinds of platelet disorders and certain kinds of vasculitis. These compounds may also be used in the therapeutic treatment of warm-blooded animals having nonimmunologic diseases such as paroxysmal nocturnal hemoglobin-urea, hereditary angioneurotic edema and inflammatory states induced by the action of bacterial or lysosomal enzymes on the appropriate complement components as, for example, inflammation following coronary occlusion. They also may be useful in the treatment of transplant rejection and ulcers and as blood culture and transport mediums. The sulfated compounds of this invention such as the sodium and aluminum salts, may be particularly useful in the treatment of ulcers and the like on oral therapy. Also, the non-sulfated intermediate compounds of Formula II may be useful as immuno-enhancing agents or potentiators.

The compounds of this invention may be prepared according to the following flowchart. ##STR3##

In accordance with the above flowchart an acetobromomaltose (1) is reacted with 4-aminothiophenol (2) and sodium hydride in a solvent such as tetrahydrofuran at reflux for 10-20 hours, giving 4-aminophenyl 2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-.alpha.(or .beta.)-D-glucopyranosyl)-1-thio-.alpha.(or .beta.)-D-glucopyranoside (3), which is then reacted with phosgene in a mixture of toluene and pyridine for 15-25 hours then purified by chromatography, giving N,N'-bis[4-[[2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-.alpha.(or .beta.)-D-glucopyranosyl)-.alpha.(or .beta.)-D-glucopyranosyl]thio]phenyl]urea (4), which is then reacted with methanol saturated with ammonia at -5.degree. to +5.degree. C., giving N,N'-bis-[4-[[4-O-(.alpha.(or .beta.)-D-glucopyranosyl)-.alpha.(or .beta.)-D-glucopyranosyl]thio]phenyl]urea (5), which is then reacted with triethylamine-sulfur trioxide in dry N,N-dimethylacetamide at 60.degree.-70.degree. C. for 40-60 hours giving (6), where X is SO.sub.3 NH.sup.30 (C.sub.2 H.sub.5).sub.3, which is then, if desired, reacted with a cation-containing compound wherein the salt forming moiety is selected from the group consisting of alkali metal, alkaline earth metal, aluminum, ammonia and substituted ammonia selected from the group consisting of piperidine, pyrazine, alkanolamine (C.sub.2 -C.sub.6) and cycloalkylamine (C.sub.3 -C.sub.6), and thereafter precipitated in ethanol, giving the end product (6) of this invention.

It is generally preferred that the respective product of each process step, described hereinabove, is separated and/or isolated prior to its use as starting material for subsequent steps. Separation and isolation can be effected by any suitable purification procedure such as, for example, evaporation, crystallization, column chromatography, thin-layer chromatography, distillation, etc. Also, it should be appreciated that when typical reaction conditions (e.g., temperatures, mole ratios, reaction times) have been given, the conditions which are both above and below these specified ranges can also be used, though generally less conveniently.

The term "pharmaceutically acceptable salt" refers to those salts of the parent compound which do not significantly or adversely affect the pharmaceutical properties (e.g., toxicity, effectiveness, etc.) of the parent compound. The salt forming moieties of the present invention which are pharmaceutically acceptable include the alkali metals (e.g., sodium, potassium, etc.); alkaline earth metals (e.g., calcium, etc.); aluminum; ammonia; and substituted ammonia selected from the group consisting of trialkylamine (C.sub.1 -C.sub.6), piperidine, pyrazine, alkanolamine (C.sub.2 -C.sub.6) and cycloalkylamine (C.sub.3 -C.sub.6).

The term "trialkylamine (C.sub.1 -C.sub.6)" defines those amines having three aliphatic fully saturated hydrocarbon substituents containing 1 to 6 carbon atoms either linearly or branched. Typically, these amines are trimethylamine, triethylamine, tripropylamine, dimethylethylamine, dimethyl-1-propylamine, etc. The term "alkanolamine (C.sub.2 -C.sub.6)" refers to the above-defined trialkylamines additionally substituted with at least one and not more than three hydroxy groups on at least two of the alkyl hydrocarbon chains. Such amines are, for example, triethanolamine, tripropanolamine, etc. The term "cycloalkylamine (C.sub.3 -C.sub.6)" is defined as the 3 to 6 fully saturated carbocyclic moieties such as cyclopropyl, methylcyclobutyl, cyclopentyl, cyclohexyl, etc.

As used hereinabove and below unless expressly stated to the contrary, all temperatures and temperature ranges refer to the centrigrade system and the terms "ambient" or "room temperature" refer to about 25.degree. C. The term "percent" or "(%)" refers to weight percent and the terms "mole" and "moles" refer to gram moles. The term "equivalent" refers to a quantity of reagent equal in moles to the moles of the preceding or succeeding reactant recited in the Preparation or Example in the term of moles of finite weight or volume.

Whereas the exact scope of the instant invention is set forth in the appended claims, the following specific examples illustrate certain aspects of the present invention. However, the examples are set forth for illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims.

A further understanding of the invention can be obtained from the following non-limiting Preparations and Examples.

To a slurry of 0.6 g of hexane-washed sodium hydride (50% oil dispersion) in 50 ml of dry dimethoxyethane was added a solution of 1.7 g of 4-aminothiophenol in 25 ml of dry dimethoxyethane. The mixture was stirred for 1/2 hour, then 8.7 g of acetobromomaltose in 20 ml. of dimethoxyethane was added. This solution was stirred overnight, then refluxed for 7 hours. The reaction was filtered and the filtrate was extracted with 50 ml of 10% sodium carbonate and 50 ml of water. The organic layer was dried, concentrated to a solid which was purified by chromatography, giving 4.1 g of the desired compound [.alpha.].sub.D.sup.26 =+44.degree. (CHCl.sub.3).

To a solution of 21.4 g of 4-aminophenyl 2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-.alpha.-D-glucopyranosyl)-1 -thio-.beta.-D-glucopyranoside in 200 ml of toluene and 25 ml of pyridine there was added 5.53 ml of toluene containing 1.77 g of phosgene. This mixture was stirred for 18 hours, then concentrated, dissolved in dichloromethane, washed with water, then saline, dried and reconcentrated. This concentrate was purified by high performance liquid chromatography, giving 10.3 g of the desired intermediate.

A mixture of 17.3 g of N,N'-bis[4-[[2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-.alpha.-D-gluc opyranosyl)-.beta.-D-glucopyranosyl]thio]phenyl]urea in 500 ml of methanol saturated with ammonia was stirred in an ice bath for 6 hours and then refrigerated overnight. The mixture was filtered through a sintered glass funnel and concentrated in vacuo to a foam. The foam was triturated with ethanol, filtered, washed with ethanol then ether and dried, giving 11.42 g of the desired intermediate.

A 72.0 g portion of triethylamine-sulfur trioxide complex was dissolved in 350 ml. of dry N,N-dimethylacetamide containing 72.0 g of 4 A molecular sieves. This mixture was heated at 60.degree.-65.degree. C. for 20 minutes. A 10.5 g portion of N,N'-bis[4-[[4-O-(.alpha.-D-glucopyranosyl)-.beta.-D-glucopyranosyl]thio]p henyl]urea was added and the mixture was heated at 63.degree.-65.degree. C. for 48 hours. The mixture was then cooled, filtered and the filtrate added to 4 liters of acetone and stirred giving a solid which is the tetradecatriethylammonium derivative of the title product.

This solid was dissolved in 85 ml of water containing 15.6 g of sodium acetate, stirred for 20 minutes, filtered and the filtrate slowly added to 4 liters of absolute ethanol and stirred for 1/2 hour. The resulting solid was collected, washed with ethanol and dried giving 16.22 g of the desired product as a light tan solid.

The final tablet will weigh about 325 mg. and may be compressed into buccal tablets in flat faced or any other tooling shape convenient for buccal adminsitration.

The ingredients are compressed into 5/8" flat based lozenge tooling. Other shapes may also be utilized.

The compounds of the present invention may be administered internally, e.g., orally, intra-articularly or parenterally, to a warm-blooded animal to inhibit complement in the body fluid of the animal, such inhibition being useful in the amelioration or prevention of those reactions dependent upon the function of complement, such as inflammatory process and cell membrane damage induced by antigen-antibody complexes. A range of doses may be employed depending on the mode of administration, the condition being treated and the particular compound being used. For example, for intravenous or subcutaneous use from about 5 to about 50 mg/kg/day, or every six hours for more rapidly excreted salts, may be used. For intra-articular use for large joints such as the knee, from about 2 to about 20 mg/joint/week may be used, with proportionally smaller doses for smaller joints. The dosage range is to be adjusted to provide optimum therapeutic response in the warm-blooded animal being treated. In general, the amount of compound administered can vary over a wide range to provide from about 5 mg/kg to about 100 mg/kg of body weight of animal per day. The usual daily dosage for a 70 kg subject may vary from about 350 mg to about 3.5 g. Unit doses of the acid or salt can contain from about 0.5 mg to about 500 mg.

The compounds of the present invention may also be administered topically in the form of ointments, creams, lotions and the like, suitable for the treatment of complement dependent dermatological disorders.

Moreover, the compounds of the present invention may be administered in the form of dental pastes, ointments, buccal tablets and other compositions suitable for application periodontally for the treatment of periodontitis and related diseases of the oral cavity.

In therapeutic use, the compounds of this invention may be administered in the form of conventional pharmaceutical compositions. Such compositions may be formulated so as to be suitable for oral or parenteral administration. The active ingredient may be combined in admixture with a pharmaceutically acceptable carrier, which carrier may take a wide variety of forms depending on the form of preparation desired for administration, i.e., oral or parenteral. The compounds can be used in compositions such as tablets. Here, the principal active ingredient is mixed with conventional tabletting ingredients such as corn starch, lactose, sucrose, sorbitol, talc, stearic acid, magnesium stearate, dicalcium phosphate, gums, or similar materials as nontoxic pharmaceutically acceptable diluents or carriers. The tablets or pills of the novel compositions can be laminated or otherwise compounded to provide a dosage form affording the advantage of prolonged or delayed action or predetermined successive action of the enclosed medication. For example, the tablet or pill can comprise an inner dosage and an outer dosage component, the latter being in the form of an envelope over the former. The two components can be separated by an enteric layer which serves to resist disintegration in the stomach and permits the inner component to pass intact into the duodenum or to be delayed in release. A variety of materials can be used for such enteric layers or coatings, such materials including a number of polymeric acids or mixtures of polymeric acids with such materials as shellac, shellac and cetyl alcohol, cellulose acetate and the like. A particularly advantageous enteric coating comprises a styrene maleic acid copolymer together with known materials contributing to the enteric properties of the coating. The tablet or pill may be colored through the use of an appropriate nontoxic dye, so as to provide a pleasing appearance.

The liquid forms in which the novel compositions of the present invention may be incorporated for administration include suitable flavored emulsions with edible oils, such as, cottonseed oil, sesame oil, coconut oil, penaut oil, and the like, as well as elixirs and similar pharmaceutical vehicles. Sterile suspensions or solutions can be prepared for parenteral use. Isotonic preparations containing suitable preservatives are also desirable for injection use.

The term "dosage form", as described herein, refers to physically discrete units suitable as unitary dosage for warm-blooded animal subjects, each unit containing a predetermined quantity of active component calculated to produce the desired therapeutic effect in association with the required pharmaceutical diluent, carrier or vehicle. The specification for the novel dosage forms of this invention are indicated by characteristics of the active component and the particular therapeutic effect to be achieved or the limitations inherent in the art of compounding such an active component for therapeutic use in warm-blooded animals as disclosed in this specification. Examples of suitable oral dosage forms in accord with this invention are tablets, capsules, pills, powder packets, granules, wafers, cachets, teaspoonfuls, dropperfuls, ampules, vials, segregated multiples of any of the foregoing and other forms as herein described.

The complement modulating activity of compounds of this invention has been demonstrated by one or more of the following identified tests: (i) Test Code 026 (C1 inhibitor)--This test measures the ability of activated human C1 to destroy fluid phase human C2 in the presence of C4 and appropriate dilutions of the test compound. An active inhibitor protects C2 from C1 and C4; (ii) Test Code 035 (C3-C9 inhibitor)--This test determines the ability of the late components of human complement (C3-C9) to lyse EAC 142 in the presence of appropriate dilutions of the test compound. An active inhibitor protects EAC 142 from lysis by human C3-C9; (iii) Cap 50 Test--Here, appropriate amounts of the test compound are added to a pool of guinea pig or human serum in vitro, after which the undiluted serum capillary tube assay of U.S. Pat. No. 3,876,376 is run. The concentration of compound inhibiting 50% is reported and (iv) Guinea Pig Intraperitoneal Test (GPIP)--Guinea pigs weighing about 300 g are dosed intraperitoneally (i.p.) with 200 mg/kg of the test compound dissolved in saline and adjusted to pH 7-8. Approximately 0.4 ml blood samples, taken by orbital sinus puncture 2 hours and 6 hours after injections, are collected directly into centrifuge tubes; 5 ml blood samples, taken by decapitation 24 hours after injection are collected directly into beakers. The samples are allowed to clot, centrifuged, and the resultant sera are assayed for complement activity using the capillary complement assay. Percent inhibition is calculated by comparison with simultaneous controls. The results of the GPIP appear in Table I together with results of Test Code 026, 035, and Cap 50. Table I shows that the principal compounds of the invention possess highly significant complement inhibiting activity in warm-blooded animals.