Dec 1 (Reuters) - Nikola Corp’s stock extended its recent drop on Tuesday as investors were allowed to sell shares of the electric truck maker on the expiration of the startup’s share lock-up period. The stock was down 15.2% and on track for a fourth straight session of declines. At early afternoon on Tuesday, about $1 billion worth of Nikola’s shares had been traded on U.S. exchanges, compared with a daily average of about $1.9 billion over the past five sessions, according to Refinitiv data. In the latest blow to Nikola, shares sold off Monday after General Motors Co scrapped its deal with Nikola that involved an equity stake in the startup and plans for building Nikola’s Badger electric pickup truck. It replaced it with a non-binding agreement that focuses on fuel-cell partnership. ADVERTISEMENT Analysts at RBC cut their price target on the stock by $2 to $17 following the news. The stock was last trading at $17.31. Nikola’s former boss Trevor Milton owns most of Nikola’s locked up shares, and under Securities and Exchange requirements would need to file notice within two business days following a sale of his shares. Milton stepped down as executive chairman in September following a squabble with short-seller Hindenburg Research over allegations of nepotism and fraud. The short-seller report came days after GM first said it would help scale up Nikola’s Badger electric pickup production and take an 11% stake and $700 million, putting the deal under scrutiny. ADVERTISEMENT As of Monday, Nikola’s short-sellers were profitable in 2020, with a net-of-financing mark-to-market profit of $309 million for the year, according to a report Monday from Ihor Dusaniwsky, managing director of predictive analytics at S3 Partners. “More stock loan supply coming from Trevor Milton’s potential stock sales should ease the pressure on stock loan rates but also help drive down its stock price as well,” Dusaniwsky noted. Shares of Nikola had surged to a record high of $93.99 in early June after Milton announced the company would start taking reservations for its highly anticipated Badger pickup. Reporting by Caroline Valetkevitch in New York and Eva Mathews in Bengaluru; Editing by Lisa Shumaker