In a regulatory filing today, Avis Budget Group Inc. said it is dropping its bid for Dollar Thrifty Automotive Group because of “current market conditions.”

Avis Budget Group’s offer, made in September 2010, consisted of a combination of $45.79 in cash and 0.6543 shares of common stock per Dollar Thrifty share, or approximately $1.5 billion in aggregate based on stock prices at the time.

Since that September 2010 offer, Hertz launched an exchange offer to purchase Dollar Thrifty for a combination of cash and stock for $72.00 per share consisting of $57.60 in cash and 0.8546 shares of Hertz.

Hertz Global Holdings Inc. is still in the running to buy the company.

In the regulatory filing, Avis Budget stated, “We have made significant progress toward obtaining U.S. regulatory clearance for the acquisition of DTG, and we believe that such regulatory clearance could be obtained. Nonetheless, we have decided not to pursue a transaction at this time in light of current market conditions.”

Last month Dollar Thrifty sent a letter to both companies asking them to submit “their best and final offers.” Dollar Thrifty had set a deadline of October 10 for both the companies to make their final buyout offers.