Anti-cancer compounds

Details Anti-cancer compounds Anti-cancer compounds

2000-07-28

2002-08-13

Tate, Christopher R. (Department: 1651)

Drug, bio-affecting and body treating compositions

Plant material or plant extract of undetermined constitution...

C424S195180

Reexamination Certificate

active

06432452

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
The present application was filed under 35 U.S.C. §371 based on PCT/AU98/00656, filed on Aug. 19, 1998, which claims the benefit of priority to Australian Application No. PO-8640, filed Aug. 19, 1997. These applications are explicitly incorporated herein by reference in their entirety and for all purposes.
This invention relates to a compound or group of compounds present in an active principle derived from the family Euphorbiaceae, and in particular in plants of the species
Euphorbia peplus, Euphorbia hirta
and
Euphorbia drummondii
. Extracts from these plants have been found to show selective cytotoxicity against several different cancer cell lines. Compounds present in the sap of Euphorbia spp. are useful in effective treatment of cancers, particularly malignant melanomas and squamous cell carcinomas (SCCs)
BACKGROUND OF THE INVENTION
There is a strong association between exposure of the skin to the ultraviolet light component of sunlight and the development of skin cancers, such as malignant melanoma and the non-melanoma skin cancers, mainly basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs). The incidence of these cancers has been rapidly increasing world wide. In Britain, there were 4000 newly-diagnosed cases of malignant melanoma in 1994, an 80% increase over the past 10 years (Wessex Cancer Trust, 1996). In the United States, approximately 34,100 new cases were expected, an increase of 4% per year. Queensland, Australia, has the highest incidence of melanoma in the world, but early detection and widespread public health campaigns and the promotion of the use of sunscreens and reduction of ultraviolet exposure have helped to reduce the number of deaths. BCCs currently affect one in 1,000 in the U.K. population, and the incidence has more than doubled in the last 20 years (Imperial Cancer Research Fund, U.K., 1997). One million new cases of BCCs and SCCs are expected to be diagnosed in the USA in 1997, compared to 600,000 in 1990 and 400,000 in 1980 (National Oceanic and Atmospheric Administration U.S.A., 1997). In Australia, there is no reason to suspect that a similarly increasing incidence would not also apply, despite extensive publicising of the dangers of solar and UV radiation, with the Queensland population being at the greatest risk.
Over 90% of all skin cancers occur on areas of the skin that have been regularly exposed to sunlight or other ultraviolet radiation, with U.V.B. responsible for burning the skin and associated with malignant melanomas, and U.V.A. associated with premature skin aging and the development of BCCs and SCCs (Wessex Cancer Trust, 1996). Childhood sun exposure has been linked to the development of malignant melanoma in younger adults. Other risk factors include a genetic predisposition (fair complexion, many skin moles), chemical pollution, over-exposure to X-rays, and exposure to some drugs and pesticides. Depletion of the ozone layer of the stratosphere is considered to contribute to long-term increases in skin cancer.
Surgical removal is by far the most common treatment for malignant melanomas, BCCs and SCCs. This can take the form of electrodesiccation and curettage, cryosurgery, simple wide excision, micrographic surgery or laser therapy. Other treatments, used when the cancers are detected at a later stage of development, are external radiation therapy, chemotherapy or to a lesser extent bio-immunotherapy or photodynamic therapy. The choice of treatment is dependent on the type and stage of the disease and the age and health of the patient (National Cancer Institute, U.S.A., 1997).
All of the present treatments suffer from severe limitations. The major concern is the poor recognition of cancerous cells at the site of excision and the high likelihood of recurrence, necessitating follow-up surgery and treatment, with the risk of further disfigurement and scarring. In one publication, the reported rates for incompletely-excised BCCs was 30-67% (Sussman and Liggins, 1996). Immune suppression associated with surgery may cause any remaining cells to proliferate, and increase the risk of metastases. In melanoma patients there is a high risk that the cancer has already metastasized at the time of initial surgery, and late recurrence leading to death is common. Present alternatives to surgery, such as radiation therapy and chemotherapy, also carry risks of immune suppression and poor specificity. Immunotherapy and gene therapy hold the greatest promise, but the rational application of these is likely to be still decades away.
When the tumour is past the stage amenable to surgery, the most common treatment for melanoma or metastatic skin cancer of all types is chemotherapy, which has been largely unsuccessful (Beljanski and Crochet, 1996)
In theory, an ideal drug would be one that when applied topically to an exposed melanoma, BCC or SCC, selectively necrotises the tumour cells or induces them to undergo apoptosis, without causing damage to the surrounding healthy skin cells. In practice, this has yet to be achieved. The drugs currently available are neither selective nor penetrative.
The lay public is also enamoured of the concept of topical chemotherapy. There have been many documented “home remedies” for skin cancer, which have had disastrous consequences, eg the use of boot polish (Adele Green, Queensland Institute of Medical Research, pers. Comm.) The major danger is the production of scar tissue, underneath which the tumour cells continue to grow. An extract derived from plants of the genus Solanum (kangaroo apple or devil's apple) and purportedly containing solasodine glycosides has been available in Australia as a non-prescription preparation treatment of sunspots and solar keratoses, under the name “Curaderm”. However the preparation was shown in a small clinical trial against BCCs to be ineffective, with 14/20 patients showing persisting tumour on histological examination of tissue from the treated site. In some cases, histological examination of the site of treatment revealed malignant tissue embedded in scar tissue. The authors warned against self-diagnosis and treatment, particularly with irritant substances (Francis et al, 1989).
However, anecdotal reports suggest that plant sap extracts are still being used by the general public for the treatment of sunspots or solar keratoses, with some success being claimed.
The sap of plants of the family Euphorbiaceae, particularly the genus Euphorbia, has been used in the folk medicine of many countries. The genus was named after an early Greek physician in deference to its purported medicinal properties (Pearn, 1987). Only recently have some of these claims been investigated scientifically. The genus is enormously diverse, ranging from small, low-growing herbaceous plants to shrubs and trees. Nearly all reports of activity of these plants and their extracts are anecdotal or derived from traditional medicine, and the nature of the preparations used is frequently either unknown or very poorly described. Activity has been claimed against a huge variety of conditions, ranging from warts, “excrescences”, calluses, “cheloid tumours”, corns, whitlows or felons, “superfluous flesh” and the like, to a variety of cancers (see, for example, Hartwell: Lloydia 1969 32 153).
As part of the screening program for anti-cancer activity carried out on 114,000 extracts from 35,000 terrestrial plant species carried out by the United States National Cancer Institute, a number of species of Euphorbia were tested. An aqueous suspension, an olive-oil suspension, an alcohol extract and an acid extract were screened for activity against the transplantable tumour cell line sarcoma 37. Four species were tested. Of these,
Euphorbia peplus
showed no activity in any of the extracts;
Euphorbia drummondii, Euphorbia pilulifera
, and
Euphorbia resinifera
showed weak activity of an acid extract, an alcohol extract, and an olive-oil suspension respectively (Belkin and Fitzgerald, 1953). A review of the scientific and medical literature of the past five years

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