Treatment of melanoma by passive humoral immunotherapy using antibody drug synergism

Targeting potential of antibody conjugates

Although the use of conjugates of enzymes has been considered, their use has not been very actively pursued. Much more interest has focused on the possibilities offered by the use of toxins, their subunits or of ribosome inhibitors. Conjugates of holotoxin which were very active and specific in vitro have been prepared. High in vivo activity and some specificity together with reduced whole body toxicity has been described. When A chain subunits or ribosome inhibiting proteins are used, the results are more mixed. Some very active and specific conjugates are known but others have relatively low activity. The reasons for this may be associated with the particular antigen to which the antibody component is directed, the nature of the A chain or inhibitor and the type and physiological state of the target cell. Application to man seems likely in the first instance to involve the removal of undesirable cells from bone marrow transplants.

Immunotherapy of melanoma

Malignant melanoma is a disease characterized by clinical evidence of host defense, possibly immunologically mediated. It is a disease which tends to be refractory to both radiotherapy and chemotherapy. Immunotherapy has been used in three phases of the disease. 1. Intralesional immunotherapy with a nonspecific immune adjuvant in patients with local intradermal or soft tissue recurrence. This treatment produces approximately 15% regression of both injected and uninjected lesions, and about 60% regression of injected lesions only. Both clinical and laboratory evidence suggests that this regression is immunologically mediated. 2. Patients with surgical removal of all clinically demonstrable tumor, either primary disease alone or regional node recurrence, active nonspecific, and specific, immunotherapy has been used in an adjuvant setting. There is considerable controversy about the benefits accruing to such immunotherapy, but most large scale prospective and randomized studies have suggested that if benefit does result it is modest in degree and probably cannot be measured in terms of increase in cure rate. 3. Immunotherapy has also been used as a nonspecific active adjuvant to single drug or polychemotherapy in patients with disseminated melanoma. Whereas complete response rate may be slightly increased by this maneuver there is no convincing evidence that immunotherapy markedly increases the total objective response rate to polychemotherapy, and survival is only marginally superior when immunotherapy is added to chemotherapy in this setting. Further studies need to be done with active specific immunotherapy with tumor cell membrane extracts; as an adjuvant in patients with minimal body burden of tumor cells; and to study the inaction between chemotherapy and immunotherapy in this disease. Furthermore, studies of chemically defined fractions of either bacterial cell wall or tumor cell extracts must be evaluated both in terms of their ability to augment cell mediated immune responses in the melanoma patient, and also in terms of their ability to induce objective benefit for the patient. The possible use of immunotherapy in patients with primary melanoma has been briefly explored but needs further study. Possible additive effects with radiotherapy and immunotherapy should also be looked at in this disease utilizing high dose fractions and other new forms of radiotherapeutic technique.