TOKYO — Japan’s Cosmo Energy Holdings made waves with the unusual type of shareholder vote it used to pass a takeover defense measure while excluding activist investor Yoshiaki Murakami, whose opposition may otherwise have doomed the proposal.

The so-called poison pill allows Cosmo to dilute the stake held by a Murakami-led group of investors if it seeks to buy more shares under certain conditions. It was approved at a general meeting Thursday with 59.54% support, according to a report filed Friday by Cosmo.

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