Membrane phenotype and response to deoxycoformycin in mature T cell malignancies.

The adenosine deaminase inhibitor deoxycoformycin was used in low doses to treat 19 patients with clinically aggressive T cell malignancy with a mature membrane phenotype. The patients comprised eight with prolymphocytic leukaemia, two with chronic lymphocytic leukaemia, four with adult T cell leukaemia-lymphoma, three with Sézary syndrome, and two with T cell lymphoma. Two thirds of the patients had been resistant or minimally responsive to combination chemotherapy. Complete remission was obtained in five patients (two with prolymphocytic leukaemia and one each with chronic lymphocytic leukaemia, adult T cell leukaemia-lymphoma, and Sézary syndrome) and partial remission in two others. Unmaintained complete remission lasting more than one year was seen in three patients. Responses were obtained only in patients with CD4+,CD8-membrane markers (seven out of 10), and no responses were recorded in any of the nine patients with a different phenotype. In this series remission appeared to correlate with the membrane phenotype of the neoplastic cell and not with the cytopathological diagnosis. Future studies should establish the biochemical basis for the greater sensitivity of CD4+ lymphoid cells to deoxycoformycin.