Private equity firm Insight Venture Partners is nearing a deal to buy influential investor advisory firm Institutional Shareholder Services, according to people familiar with the matter.

MSCI, the financial index provider that owns ISS, announced in October that it was exploring "strategic alternatives" for the business. Insight is the likely winner of an auction MSCI ran, the people said. Terms of the potential deal, and when it might be announced, couldn't be learned.