Opthea (ASX:OPT) has terminated phase three clinical trials for two of its drug candidates following negative results, according to a Thursday Australian bourse filing.

The company will be reducing its workforce by about 65% to cut costs while retaining a limited number of employees to ensure compliant termination of clinical trial activities and oversee administrative operations, the filing added.

The company expects the workforce reduction to take effect from May 1 with one-off costs of about $4.5 million, resulting reduction in monthly employee costs of $1 million.

The company sees unaudited cash and cash equivalents of $100 million at the end of March.

The company said its ability to continue as a going concern remains materially uncertain.