1. Field of the Invention
The present invention relates to a method for preparing a therapeutic agent from placenta.
2. Description of the Prior Art
To date, many publications have been concerned with methods of extracting physiologically or pharmacologically active substances or purifying the placental extract. Some of these extracts have been reported to possess anti-ulcer or anti-cancer effects. None, of the reported prior art placental extract preparations have been shown to possess leukemia therapeutic effects.
Hieda ("REIZOTAIBAN NO SEIKAGAKU TO IRYOKOKA" or "The bio-chemistry and therapeutic effect of frozen placenta" Kinbara Shoten, 1965) reported the presence of a substance in human placenta which is effective against cirrhosis. Kumura (HIROSHIMA IGAKU 22 (12), 1136, 1969) and Saito (Clinical report 3 (7), 543, 1969) described a placenta preparation which possesses anti-ulcer effects. Also, Byong Ho Chin (Abstract of Papers of the 9th International Cancer Congress, 467 pp, 1966) communicated an anti-Ehrlich sarcoma agent and an anti-N-F sarcoma agent from human placenta.
Hieda's preparation against the cirrhosis was obtained as follows:
A fresh placenta was washed with water, permitted to stand at 2.degree. - 4.degree. C for several days, minced, and boiled for 60 min. The preparation was admixed with 1 N HCl in an amount of 1/5 its volume, to obtain a pH of 1.8. It was then digested with 2 g of pepsin at 38.degree. C for 20 hours. The digested fluid was centrifuged at 3,000 r.p.m. for 15 min. to separate the supernatant from the precipitate. The supernatant was passed through an ion exchange resin to reduce its acidity to pH 4.4 - 4.6 and its volume was increased to 100 ml for every 100 g (wet weight) of placenta by the addition of water. This preparation was referred to as Solution A. The precipitate was hydrolysed with concentrated hydrochloric acid by heat treatment over a period of 10 hours. The hydrolysate was succeedingly decolorized with activated carbon, the excess volatile acid removed by evaporation on a water bath, and then subjected to secondary decolorization. The acidity of the solution was reduced with an ion exchange resin to pH 4.4 - 4.6. The volume of the eluate was made up so that every 100 g (wet weight) of placenta gave the volume of 25 ml. This preparation was referred to as Solution B. Solutions A and B were blended and the acidity of the mixture was adjusted to pH 6.1 - 6.4. Following boiling and clarification by filtration, the preparation was poured into an injection ampoule, and the solution was sterilized for use. The preparation was a transparent and yellow-colored solution, had a specific gravity of 1.0090 - 1.0132, pH of 6.1 - 6.4, showed a negative sulfosalicylic acid test and contained 78.6 - 82.3 mg/ml in dry matter. The ash, total nitrogen and amino nitrogen contents were 8.0 - 9.3 mg/ml, 9.13 - 11.21 mg/ml and 8.56 - 10.24 mg/ml respectively. The extract was claimed to possess lipotropic activity and to be capable of enhancing tissue respiration of the liver, stimulation of the thyroid gland, and basal metabolism of castrate animals. It was also reportedly useable for cirrohosis therapy, in humans and for experimental standard test animals.
Boyous Ho Chin prepared an emulsion of placenta and centrifuged it to obtain the supernatant. With addition of alcohol, a precipitation was obtained, which was subjected to fractionation by means of paper electrophoresis. The resultant fraction was dialysed against water and the dialysate or non-dialysable fraction was further subjected to precipitation with acetone. The author claimed that this precipitate possessed inhibitory effects on the growth of Ehrlich sarcoma and N-F sarcoma.
It is of consequence to note that none of the previously prepared placental extracts were found to possess therapeutic effects against leukemia, as shown by the description vide infra.
On the other hand, Carbazilquinone (Arakawa, M. et al Gann, 61 485, 1970), cytosine arabinoside (Talley, K. et al. Blood 21 352, 1963), Daunomycin (Tan, C. et al, cancer 20 333, 1967), Adriamycin (Di Marco, A. et al. Cancer Chemotherapy reports 53 33, 1969), L-asparaginase (Kidd, G. G. et al. Journal of Experimental Medicine 98 565, 1953) are among known anti-leukemic agents. These materials are extracted from natural sources, however, other than the placenta, or they have been chemically synthesized. However, all the anti-leukemic agents, so far known and used, are not specific in effect to the leukemic cells, but are observed clinically to give rise to various undesirable side effects, such as leucopenia, thrombocytopenia, anemia, hemorrhage, vomitting, diarrhea, fever, renal lesion, hepatic lesion, jaundice, etc. Therefore, therapeutic use of these prior art materials also required auxiliary care in order to prevent such inevitable complications. Acceptable therapeutic results have, therefore, not been fully achieved, due to the quite serious complications derived from the side effects. Chemotherapy for leukemia at the present time is therefore, only capable of leading to a remission of the disease, but this is achieved by a trade-off between longer survival and host toxicity, but complete cure has not been possible.