Experimental and clinical studies with a new antimonial preparation for the treatment of schistosomiasis

Bull. Org. mond. Sante 1971, 45, 411-417Bull. Wid Hith Org. Experimental and Clinical Studies with a New Antimonial Preparation for the Treatment of Schistosomiasis MIGUEL RON PEDRIQUE 1 & NICOLO ERCOLI 2 This paper presents the results ofa clinical study in which a new antimony preparation- a chelate of dimethylcysteine with antimony sodium tartrate (" NAP")-was administered intramuscularly at a total dosage of 2 g (5 x 400 mg, corresponding to 290 mg of Sb) to 400 patients with schistosomiasis. Among 108 patients in a rural population the treatment was on the whole well accepted (97 % completed the intensive course of injections), thus indicating that NAP would be useful for the mass treatment of'schistosomiasis. Penicillamine-dimethylcysteine (DMC)-detoxi- fies both arsenicals and antimonials without impair- ing their antiparasitic action. This phenomenon of selective antagonism (Ercoli, 1967), not observed in analogous structures, was discovered in 1963 and utilized for the preparation of chelate compounds with both antimony potassium tartrate and anti- mony sodium tartrate. The formula assigned to the chelate formed with the latter tartrate is as follows: COOH CH3 CHO ~ ~~-S C CH3 | Sb_ I CHO- --NH- CH I I COONa COOH The pharmacological and chemotherapeutic stu- dies that preceded the clinical trials reported on here (Ercoli, 1968b) showed that the above compound, when complexed with an additional amount ofDMC, was rendered less toxic while retaining its efficacy. An extensive physicochemical study of this DMC complex carried out recently by Barber et al. (1969) 1 Profesor (Titular) de Clinica Medica, Escuela de Medi- cina J. Vargas, Universidad Central de Venezuela; Director, Servicio Anti-bilharziano del Ministerio de Sanidad y Asis- tencia Social, Caracas. ' Profesor (Titular) de la Facultad de Ciencias, Jefe del Grupo de Investigaci6n de Parasitologia, Instituto de Zoolo- gfa Tropical, Universidad Central de Venezuela, Caracas. has indicated that antimony is present in solution solely in the form of its complexes with DMC, the tartrate being displaced by the amino acid. Our studies relate in particular to two DMC chelates: one with antimony potassium tartrate (tartar emetic), designated TP2, which has an antimony content of 12.2%, and the other with antimony sodium tar- trate, designated NAP, which has an antimony con- tent of 14.5-15.6%. The main pharmacological data are summarized in Tables 1, 2, and 3. All the studies made in recent years have demonstrated the high schistosomicidal effect of NAP at dosages that are low in relation to their antimony content (Ercoli, 1968b; Payares, 1968; Table 1. Toxicity and therapeutic activity of DMC chelates of antimony potassium tartrate (TP1 5 and TP2) in comparison with other antimonials in mice infected with Trypanosoma equiperdum (doses are expressed in mg of Sb per kg of body weight) Curative dose ThrpuiDrug LD5o (clearing Therapeutic dose) ine antimony tartrates (K & Na) 19.5 11 (2.7) 1.8 TP15 51 14 (1.8) 3.6 TP2 73 14 (1.8) 5.2 stibophen 110 30 (4.1) 3.7 sti bocaptate 500 125 4.0 2735 - 411 - M. RON PEDRIQUE & N. ERCOLI Table 2. Toxicity and therapeutic activity of NAP in comparison with other antimonials in experimental infection of mice with Trypanosoma venezuelense (doses are expressed in mg of Sb per kg of body weight) Curative doseThrDrug LD50 (clearing Therapeutic dose) ine antimony sodium tartrate 1 9 47.6 a (3.9) 0.4 NAP 57 45 b (3.6) 1.3 stibophen 110 108 c (10) 1.0 a14 x 11.9. b)3 x 15. c 4 x 25.2. Payares & Ercoli, 1969). On the basis solely of the relative amount of antimony, tartar emetic is still the most effective drug against schistosomes. With regard to antimony content, NAP retains 80-90%0 of this activity, stibophen 35 %, and stibocaptate 10 %. It was primarily the reduction in toxicity without any significant decrease in the therapeutic effect of the antimony in DMC chelates that led to the cli- nical studies carried out since 1964. These trials can be divided into four phases: (l) clinical study of TP2, a DMC chelate of anti- mony potassium tartrate, 1964; (2) clinical study of NAP to determine the most suitable dose, 1964-66 (Ron Pedrique et al., 1966, 1967); (3) routine clinical use of NAP in a standardized form and dose, since 1967; Table 3. Toxicity and action on Schistosoma mansoni ("liver shift") of various antimonials (doses are expressed in mg of Sb per kg of body weight) Drug LD50 Shift Toxicity/ antimony tartrates (K 8 Na) 1 9.5 8 2.4 TP2 73 14 5.2 NAP 57 14 4.0 stibophen 110 30 3.7 (4) use of NAP in a rural population to investigate its value for mass treatment, 1968-69 (Ron Pedrique et al., 1970). Studies using TP2 This preparation, with an antimony content of 12.2%, was injected by the intramuscular route in 5 consecutive daily doses of 300-360 mg each per patient. The total amount of antimony injected reached 180-220 mg per patient and this led to the disappearance of eggs from the faeces of 24 of the 52 patients treated (3 stool examinations were made by the concentration method after 1, 2, 3, 6, and 12 months of treatment). The local, general, and cardiac tolerance (the last-mentioned followed up by electrocardiogram) of the preparation was excellent and this induced us to continue the trials in the belief that the limited therapeutic effect (46%) was due to the very low antimony dose used. The low solubility of TP2 (6 %) precluded its use in higher doses suitable for intensive therapy. Stludy of the preparation and dosage ofNAP For the reasons set out above, more soluble DMC chelates of antimony sodium tartrate were developed with an increased antimony content (14.5-15.60%) permitting higher doses of antimony to be used clini- cally. The product was prepared for clinical use in the form of a powder to be dissolved in 5 ml of distilled water, and the fresh solution was administered by deep intramuscular injection, repeated during 5 con- secutive days. Preliminary clinical trials were made with chelates that contained 14.5 ., 14.9 %, and 15.65 % of anti- mony, the doses for intramuscular injection being 380 mg, 400 mg, or 450 mg. The effect of treatment with these doses on the presence of eggs in the faeces, demonstrated by the concentration method (rests completed in Decem- ber 1965), is shown in Table 4. It can be seen that the effect obtained with a total dosage of either 275 mg or 298 mg of antimony in the form of NAP is considerable: an egg-clearing rate of 78 % was observed-a higher figure than that observed with stibocaptate at a dosage of 500 mg of antimony (71 %). When the NAP dosage was in- creased to a total of either 313 mg or 336 mg of anti- mony, the effectiveness of the product rose from 78% to 88.40%. 412 NEW ANTIMONIAL FOR TREATMENT OF SCHISTOSOMIASIS Table 4. Therapeutic effect of various antimonials on patients with schistosomiasis (S. mansoni): results obtained up to December 1965 I Total No. of No. of No. of negative patients Percentage Drug Sb content Single dose amount of patients patients of negative(%) (mg) Sb per treated followed up 1-3 4-12 patientspatient (mg) months months TP2 12.2 300-360 180-220 61 52 11 13 46 NAP 14.5 380 275 58 180 101 39 7814.9 400 298 1901810397 NAP 15.6 400 313 12 } 43 26 12 88.414.9 450 336 26 stibocaptate 25 400 500 95 83 59 0 71 It should be noted that, in one group of 146 patients treated with NAP at a total dosage of 298 mg of anti- mony, there were 30 (20 %) who had previously been treated unsuccessfully with antimony sodium tartrate; in 24 of these 30, the faeces were cleared of eggs after NAP treatment, as indicated by stool exami- nations made over a period of more than 3 months. In the course of all the clinical trials the utmost attention was paid to tolerance, which we regarded as the decisive factor governing the clinical useful- ness of the drug. In all, 286 patients were studied and treated in the comparative phase with different doses: (a) 190 patients with 400 mg of NAP (Sb content, 14.9 %; treatment with 25 ml corresponding to a total of 298 mg of Sb); (b) 58 patients with 380 mg of NAP (Sb content, 14.5%; treatment with 25 ml corresponding to a total of 275 mg of Sb); (c) 26 patients with 450 mg of NAP (Sb content, 14.9 %; treatment with 25 ml corresponding to a total of 336 mg of Sb); and (d) 12 patients with 400 mg of NAP (Sb content, 15.650%; treatment with 25 ml corresponding to a total of 313 mg of Sb). These patients ranged in age from 13 to 64 years, most of them being between 18 and 39 years (210/286). They were given a complete clinical examination as well as laboratory tests (faeces, urine, and the Cercarien Hiillen Reaktion [CHR] of Vogel & Minning); a cardiovascular examination, including an electrocardiogram, was also performed before and after treatment. The clinical findings were similar to those generally encountered in previous studies: pain on palpation of the colon (47 %); palpable colonic spasms (36.4 %); enlarged liver (11.9 %); and enlarged spleen (2.4%). The main symptoms mentioned at the consultation were dizzi- ness, diarrhoea, constipation, flatulence, fullness after meals, etc. 60% of the patients had been ill for more than 1-2 years. The immediate tolerance of the NAP injection was excellent; a small proportion of cases (2.7 %) presented local reactions-consisting ofredness, pain, and, in one case, vesiculation-24 hours after the initial injection. The symptoms of general intole- rance were qualitatively similar to those observed with other antimonials, i.e., vertigo and nausea, with or without vomiting, and general malaise. From the quantitative viewpoint (apart from the low fre- quency) the reactions of intolerance were very slight. The episodes of vomiting were of short duration and responded well to the administration of meclozine hydrochloride. General intolerance was more fre- quent during the first day of treatment. The relationship between the dose used and NAP tolerance is shown in Table 5. The proportion of patients without adverse reactions to a total anti- mony dose of 298 mg was 71 % after the first injec- tion and rose to 88 % after the second injection. Administration ofa standardized form and dose Once the comparative tolerance of the different doses had been determined, we standardized the treatment, using a product containing 14.5 % of antimony injected on 5 consecutive days in doses of 400 mg per patient. The 2 g of NAP injected during this treatment correspond to an antimony content of 290 mg. 413 414 M. RON PEDRIQUE & N. ERCOLI Table 5. Relationship between dose of NAP used and tolerance Patients without reaction to: Single dose amount No. of first injection second injection (m g) of patients Sb (mg) treated No. of No. of Ipatients % +SD patients % ±SD 400 298 190 135 71.1 ± 3.3 167 87.9 ± 2.1 (14.9 % Sb) 380 275 58 48 82.8 i 5 50 86.2 ± 4.5 (14.5 % Sb) 400-450 313-336 38 23 60.5 ± 7.9 29 76.3 ± 6.9 (14.9-15.65 % Sb) Total 286 206 72.0 246 86.0 So far, 400 patients have been treated in this way. The cure rate, based on stool tests of 346 patients, is 82.5±2%. In 23 of 26 patients examined a year after treat- ment, the CHR of Vogel & Minning was negative. Use ofNAP in a rural population 1 Among the group of 400 patients, 108 formed part of a special study carried out with the aim of deter- mining whether NAP satisfied the necessary psycho- logical and physical requirements for acceptance and satisfactory use in a rural environment, where the population is generally more susceptible to the draw- backs of a drug and where health consciousness is less developed. This study took place at Guatire and Guarenas in the State of Miranda. The population consists of workers and peasants who live in rustic houses, are reasonably well nou- rished, and do not seek medical treatment spontane- ously. In general, they are unfavourably disposed to antischistosomal treatment, probably for fear of the nervous symptoms induced by some of the drugs pre- viously used. It can be stated that the population in question has a certain prejudice against the intensive use of drugs with higher requirements concerning tolerance. Only patients with highly positive faeces were in- cluded in the study. Those who were pregnant, those who had heart conditions, and those suffering from serious malnutrition were excluded, as were persons under 15 or over 60 years of age. Of the 108 patients 1 Ron Pedrique et al., (1970). included in the study, 26 (14.5%) had been previously treated with other drugs (lucanthone and antimony sodium tartrate). The total number of patients completing the treat- ment was 105-i.e., 97% of those who commenced it. One of these patients received only four injections instead of five because he was absent from the locality on the day of the third injection. The 108 patients were divided into 8 groups and were treated successfully at different times between June and August 1968. After treatment of the first groups had been completed, the population became sufficiently confident to follow the treatment willing- ly. A male patient aged 37 years, a chronic alcoholic who had twice previously been intensively treated with antimony sodium tartrate, had to abandon treatment because of intolerance that became evi- dent from the first injection. The other two patients who did not complete treat- ment after the first two injections were both women (27 and 44 years of age, respectively), who developed slight reactions (nausea, anorexia, and one episode of vomiting). Between the two extremes-i.e., those patients who presented not the slightest reaction to any of the five injections and those who reacted by vomiting after every injection-the remainder of the population suffered side-effects of varying frequency, intensity, and nature: nausea, vomiting, malaise, headache, diarrhoea, or slight fever (37-380C). Evaluation of tolerance of NAP treatment was based on the following clinical criteria (Table 6): NEW ANTIMONIAL FOR TREATMENT OF SCHISTOSOMIASIS Table 6. Tolerance of rural patients treated with NAP (total dose of Sb: 290 mg)* Excellent Sex No. ofpatients M 28 F 3 M = 48 (4 F = 15(1 Good Sx INo. of_Sex patients M 20 F 12 [8/61 = 78.7 %) 5/47 = 31.9 %) Fair Poor Sx No. of Sx No. ofpatients patients M 12 M ia F 24 F 8 b M = 13 (13/61 = 21.3%) F = 32 (32/47 = 68.1 %) * Reproduced, with slight modifications, from Ron Pedrique et al. (1970), by permission of the Liver- pool School of Tropical Medicine. a Treatment was abandoned because of intolerance symptoms. b Two patients abandoned treatment after the second injection. Excellenit. Absence of any objective or subjective reaction after all five injections (19 patients) or slight subjective malaise after only one of the five injections (12 patients). Good. Reaction purely subjective (malaise) with- out symptoms, or a slight objective reaction after one or two injections (32 patients). Fair. Various slight objective symptoms (fever, diarrhoea, vomiting) in the course of treatment (36 patients). Poor. Copious vomiting (5 patients); palpitations or feeling of asphyxia (1 patient); abandonment of treatment (3 patients). The tolerance of the patients according to sex is also shown in Table 6. It appears that men tolerate the treatment better than women. The therapeutic effect, based on stool tests per- formed 1, 2, and 3 months after completion of treat- ment by means of direct observation and the concen- tration method, indicated a parasitological cure in 94% of the 101 patients followed up. In general, the rural experiment was very satis- factory from the viewpoints of tolerance, therapeutic results, and acceptability. DISCUSSION AND CONCLUSIONS Our clinical trial of NAP fully confirms the expe- rimental data, which showed a high antiparasitic activity and a favourable therapeutic index for the DMC chelates of antimony sodium tartrate. Intensive NAP treatment with a total dose cor- responding to 290 mg of antimony, which is well tolerated, gave therapeutic results considerably better than those obtained with intensive treatment with antimony sodium tartrate in a dose containing 231 mg of antimony, which causes very marked in- tolerance reactions. According to our previous experience (Ron Pedrique & Gerulewics, 1955), antimony sodium tartrate gives a low cure rate (60%). Apart from the larger total Sb dose, other factors (route of injection, period of treatment, and formulation of the drug) contribute to the greater therapeutic effectiveness of NAP (Payares & Ercoli, 1969; Ercoli & Payares, 1969). Compared with other antimonials we have used during the last 15 years in the Schistosomiasis Con- trol Service (anthiolimine, antimony sodium tartrate, stibophen, trivalent antimony sodium gluconate, and stibocaptate, in thousands of patients (Ron Pedrique & Gerulewics, 1955; Ron Pedrique, 1958), NAP shows greater effectiveness and is better tolerated. Direct comparison can be made only with antimony sodium tartrate, trivalent antimony sodium gluco- nate, and stibocaptate, the only drugs used for in- tensive treatment. NAP is not only more effective than antimony sodium tartrate, but it can be admi- nistered intramuscularly. It is more active and is considerably better tolerated than stibocaptate, doubtless owing to the smaller amount of antimony used for treatment (290 mg in NAP, 500 mg in stibocaptate) (Ercoli, 1968a; Ercoli & Ron Pedrique, 1969). Compared with trivalent antimony sodium gluconate, which is somewhat better tolerated than antimony sodium tartrate and which calls for intra- venous injection, NAP has the advantage of mani- fest therapeutic superiority, despite the fact that the first-named product was used in higher dosage (405 mg of Sb). 415 416 M. RON PEDRIQUE & N. ERCOLI We shall not make any comparisons between NAP and stibophen or anthiolimine, which are clinically toxic, not very effective, and unsuitable for intensive therapy. The behaviour of the patients treated with NAP in the rural area appeared to be particularly favour- able: most of them carried on with their ordinary work during the 5-day treatment period, only 10% of the women remaining completely inactive in their homes. The therapeutic efficacy of NAP in infections with Schistosoma mansoni has been confirmed by Hernandez and Oliver-Gonzales (1971), and in infections with S. japonicum by Santos et al. (1970). In conclusion, NAP is relatively well-tolerated, easy to administer, and highly effective for the mass treatment of schistosomiasis. For these reasons, it is superior to any of the other antimonials avail- able. RE-SUME ETUDES EXPERIMENTALES ET CLINIQUES D'UNE NOUVELLE PREPARATION STIBIHE POUR LE TRAITEMENT DE LA SCHISTOSOMIASE La penicillamine (dimethylcysteine) attenue la toxicite pour F'h6te des composes arsenicaux et antimoniaux sans modifier leur activite antiparasitaire. On a mis a profit cet antagonisme selectif pour preparer des chelates de penicil- lamine et de sels d'antimoine que l'on a soumis a des essais cliniques. Le chelate de penicillamine-tartrate d'antimoine et de potassium (TP2), contenant 12,2o% d'antimoine, a e essaye en 1964. Injecte par voie intramusculaire (dose totale d'antimoine: 180-220 mg), il a fait disparaitre les ceufs des selles pendant un an chez 24 malades sur 52. Le produit est bien tolere, mais sa faible solubilite empeche de l'utiliser a des doses plus elevees et reellement efficaces. De 1964 a 1966, on a procede a des essais cliniques avec le chelate de penicillamine-tartrate d'antimoine et de sodium (NAP), plus soluble et contenant 14,5 ah 15,60% d'antimoine. On l'a injecte a des groupes de malades a la dose quotidienne de 380 a 450 mg, representant une dose totale de 275 a 336 mg d'antimoine. Dans le groupe traite par une dose totale de 275 mg, 82,8% des sujets n'ont presente aucun signe d'intolerance; ce taux est tombe a 71 % dans le groupe recevant une dose totale de 298 mg et a 60,5% lorsque la dose a e portee a 336 mg. Dans tous les groupes, la tolerance a et meilleure apres la seconde injection qu'apres la premiere. Depuis 1967, on a uniformise le traitement: injection pendant 5 jours consecutifs d'une dose de 400 mg de NAP (14,5% d'antimoine), soit au total 290 mg d'anti- moine. Chez 346 patients ainsi traites, le taux de guerison a atteint 82,5% et la reaction de Vogel & Mining etait negative apres un an chez 23 malades sur 26. Des essais menes en 1968/69 dans une region d'endemi- cite ont confirme que le traitement etait bien tole&, favo- rablement accueilli par la population rurale et donnait un taux de guerison eleve (94% durant les 3 premiers mois suivant la fin du traitement). La tolerance a ete meilleure chez les hommes que chez les femmes. Ces etudes indiquent que le NAP peut avantageuse- ment etre utilise pour le traitement de masse de la schistosomiase. REFERENCES Barber, M. A., Kapadia, A. J. & Martin, A. E. (1969) NAP complex. A progress report (Internal Reports A. H. Robins International) Ercoli, N. (1967) Nature (Lond.), 216, 398-399 Ercoli, N. (1968a) Significado del indice quimioterdpico para el tratamiento de la bilharziosis con antimoniales. In: XIV Congreso Interamericano de Zoologia (Secci6n de Parasitologia), Caracas Ercoli, N. (1968b) Proc. Soc. exp. Biol. (N. Y.), 129, 284-290 Ercoli, N. & Payares, G. (1969) Acta cient. venez., 20, 164-167 Ercoli, N. & Ron Pedrique, M. (1969) Comparison of experimental findings and clinical antibilharzial action of antimonials. In: Fourth International Congress of Pharmacology, Basle, Abstracts 454-455 Hernandez Morales & Oliver-Gonzalez (1971) Amer. J. trop. Med. Hyg. (In press) NEW ANTIMONIAL FOR TREATMENT OF SCHISTOSOMIASIS 417 Payares, G. (1968) Actividad esquistosoinicida del anti- inonil-dinietilcisteino-tartrato (NAP). In: XIV Congreso Interamericano de Zoologia (Secci6n de Parasitologia), Caracas Payares, G. & Ercoli, M. (1969) Influencia del esquemna de tratamienito en la efectividad del sodio antimonil-dimetil- cisteino-tartrato (NAP). In: XIX Convenci6n Anual de la Asociaci6n Venezolana por Avance de la Ciencia Ron Pedrique, M. (1958) G. E. N. (Caracas), 12, 241-244 Ron Pedrique, M., Barbera, S. & Ercoli, N. (1970) Ann. trop. Med. Parasit., 64, 255-261 Ron Pedrique, M., Chacin Lander, C., Sans6n, R. E. & Arroyo, J. M. (1966) Tratamiento intramuscular de la bilharziosis con un nuevo antimonial (NAP) (Jornadas Venezolanas de Medicina Interna, Hospital Vargas, 28-30 de abril) Ron Pedrique, M., Chacin Lander, C., Sans6n, R. E. & Arroyo, J. M. (1967) Acta med. Venez., 14, 137-142 Ron Pedrique, M. & Gerulewics, E. (1955) G. E. N. (Caracas), 10, 532-550 Santos, A. T., Blas, B. L., Eugenio, L. E. & Portillo, G. P. (1970) J. Philipp. med. Ass., 5, 254-258