SAO PAULO, May 23 (Reuters) - Brazil's cancer clinic chain Oncoclinicas said late on Wednesday its board of directors has approved a private capital increase of around 1.50 billion reais ($290.96 million) through the issuance of new shares.

Oncoclinicas said in a securities filing it would issue 115.38 million new common shares priced at 13.00 reais each, a premium of 74.5% over its Wednesday closing price.

Investment funds Quiron and Tessalia, which are linked to lender Banco Master, committed to subscribe shares worth up to 1 billion reais as part of the move, Oncoclinicas said. That would take their stake in the company to 12.3%.

The firm's chief executive Bruno Ferrari, a member of Oncoclinicas' controlling block, committed to an investment of up to 500 million reais, the company added.

Goldman Sachs is also a major shareholder of Oncoclinicas.

In a separate filing, the company said it now expects its financial leverage as measured by the net debt/EBITDA (earnings before interest, taxes, depreciation and amortization) ratio to end this year at 2.0, down from 3.9 at the end of March. ($1 = 5.1554 reais) (Reporting by Luana Maria Benedito; Editing by Gabriel Araujo)