Among the winners from the recent retail-driven frenzy in US stocks are investors in the niche market of convertible debt, capping a year of gains for the securities and potentially drawing new interest.

While buyout firm Silver Lake capitalised on a surge in AMC Entertainment, one of the stocks at the epicentre of the retail frenzy linked to a convertible bond, others have also seen their bonds gain.

Those holding convertible notes - which allow investors to convert the debt to equity when a company's shares hit a set price - in Ligand Pharmaceuticals have seen prices...