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Transient Retinal Effects of 5,6-Dimethylxanthenone-4-acetic Acid (DMXAA, ASA404), an Antitumor Vascular-Disrupting Agent in Phase I Clinical Trials

¹From the Regional Cancer Centre, Waikato Hospital, Hamilton, New Zealand; the ²Departments of Ophthalmology and ⁴Oncology, Auckland City Hospital, Auckland, New Zealand; ³Moorfields Eye Hospital, London, United Kingdom; the ⁵Department of Pharmacology and Clinical Pharmacology and the ⁹Auckland Cancer Society Research Centre, University of Auckland, Auckland, New Zealand; the ⁶Oncology Service, Christchurch Hospital, Christchurch, New Zealand; the ⁷Drug Development Office, Cancer Research UK, London, United Kingdom; and ⁸Antisoma Research Limited, London, United Kingdom.

PURPOSE. 5,6-Dimethylxanthenone-4-acetic acid (DMXAA), an anticancer vascular-disrupting agent, has induced transient visual symptoms in some patients. Exploratory investigations were undertaken to characterize the visual disturbances in two consecutive phase I trials.

METHODS. Assessments were made in 21 patients before and immediately after a 20-minute IV infusion of DMXAA, including visual acuity, funduscopy, color discrimination, pattern electroretinography (PERG), pattern visual-evoked potentials (VEP), and full-field electroretinography (ERG). Evaluation of late effects was undertaken subsequently in 12 patients before and after 6 weeks of IV DMXAA at one dose per week.

RESULTS. Frequency and intensity of transient visual disturbance increased with DMXAA dose, occurring in two thirds of patients at 3000 mg · m^–2. Symptoms included blurring, flickering, fragmentation, alteration of colors, and contrast and mild photosensitivity, starting during the infusion and resolving completely, usually within 60 minutes. Visual acuity was unchanged but color discrimination was perturbed. Dose-dependent increases in PERG P50 implicit time by up to 23 ms returned toward baseline values within 90 minutes. Prominent transient changes on ERG included prolonged scotopic rod and 30-Hz flicker implicit times and reduced 30-Hz flicker amplitude. In the second trial, no clinically significant sustained effects were detected, although an increase in bright flash a-wave implicit time (P = 0.022) was seen on whole-group analysis. In vitro studies showed nonspecific phosphodiesterase inhibition by DMXAA.

CONCLUSIONS. DMXAA induced acute, transient disturbance of retinal activity consistent with phosphodiesterase inhibition. No clinically significant cumulative effects were noted and most effects occurred at doses higher than those used in ongoing clinical trials (ClinicalTrials.gov numbers, NCT00856336, NCT00863733, and NCT00003697).