PHTHALOCYANINE PHOTOSENSITIZATION FOR IN VITRO ELIMINATION OF RESIDUAL ACUTE NON‐LYMPHOBLASTIC LEUKAEMIA: PRELIMINARY EVALUATION

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Abstract
Autologous bone marrow transplantation (ABMT) in first remission of acute non‐lympho‐blastic leukaemia (ANLL) has increased the proportion of patients eligible for intensive myeloablative therapy and has produced encouraging early results. However, more patients relapse after ABMT than after allogeneic BMT and this may be due in part to reinfusion of leukaemia with the graft. We have examined the phototoxicity of sulphonated chloro‐aluminium phthalocyanine (SPC) on leukaemic blasts from patients with ANLL and normal myeloid progenitors (GM‐CFC) to determine whether in vitro phototherapy might be used to eliminate residual ANLL from bone marrow grafts. ANLL blasts were shown to take up SPC readily and the phototoxicity was shown to be dependent on the concentration of SPC, duration and temperature of incubation, the interval from SPC incubation to light exposure and the duration of light exposure using 675 nm light delivered by an optical fibre at 50 mV from an Ar pumped dye laser. After a 2 hour incubation at 25 μ.g SPC m−1 recovery of ANLL blasts at 24 h was 5 ± 2% whilst GM‐CFC recovery from normal marrow was 47 ± 9%. This study suggests that ANLL blasts may be more sensitive to SPC phototoxicity than normal marrow GM‐CFC, and further studies to examine the potential of this compound for the elimination of residual ANLL from marrow autografts are in progress.