4 fixed dosing levels (0.25 -0.5mg) of Topotecan will be evaluated in this trial, using sub-cytotoxic doses of Topotecan which are well below typical chemotherapy levels and shown not to cause myelosuppression in previously tested populations. The dose escalation will be in a standard 3+3 dose escalation design with 0.25 mg increments of Topotecan. The study aims to establish the recommended phase 2 dose (RP2D) of Topotecan in hypoxic patients with moderate to severe COVID-19.The RP2D is defined as the maximum safe dose at which 3 or more patients are found to have clinically relevant concentrations of Topotecan in the blood stream, without reaching anti-cancer concentrations in plasma (defined as Area under the curve (AUC)>150000) and without causing Grade 2/3/4 neutropenia (CTCAE5).
The primary objective of the phase 1 trial is to identify a dose of topotecan that will be safe to take forward into a Phase 2 trial, with no unexpected toxicities or drug-drug interactions with standard therapy for COVID-19. The investigators hypothesise that a single dose of low-dose Topotecan will blunt the expression of inflammatory genes in patients with moderate COVID-19, without cytotoxic side effects.