Analyst Upgrades: Amazon.com, Inc., MBIA Inc., and Pfizer Inc.

Analysts are weighing in on Internet retailer Amazon.com, Inc. (NASDAQ:AMZN), insurance issue MBIA Inc. (NYSE:MBI), and pharmaceutical blue chip Pfizer Inc. (NYSE:PFE). Here's a quick roundup of today's bullish brokerage notes on AMZN, MBI, and PFE.

• As of last night's close at $628.35, AMZN shares have more than doubled year-to-date, boosted by a recent earnings beat. Despite receiving a price-target lift to $800 from $725 at Deutsche Bank overnight, though, the stock is pointed 0.3% lower pre-market. In recent months, option traders have been gambling on losses for Amazon.com, Inc., per data from the International Securities Exchange (ISE), Chicago Board Options Exchange (CBOE), and NASDAQ OMX PHLX (PHLX). Specifically, the equity's 50-day put/call volume ratio of 1.07 ranks in the bearish 92nd percentile of its annual range. In other news, AMZN will be opening its first physical bookstore today in Seattle, called Amazon Books, and announced an expanded family-leave policy (subscription required) to attract and retain talent.

• MKM Partners boosted its assessment of MBI to "buy" from "neutral," ahead of the company's third-quarter earnings report tomorrow night. The bullish note has the shares up 2.7% ahead of the bell, as they try to claw their way back from a nearly 19% year-to-date deficit, as of Monday's close at $7.74. Option players have been rolling the dice on post-earnings upside for MBIA Inc., buying to open more than 18 calls for every put during the past two weeks. The corresponding ISE/CBOE/PHLX call/put volume ratio of 18.13 registers a mere 6 percentage points from a 12-month peak.

• Amid reports that GlaxoSmithKline plc (ADR) (NYSE:GSK) rebuffed a PFE buyout attempt prior to the latter's talks with Allergan PLC (NYSE:AGN), shares of the blue chip saw their price target raised to $41 from $40 at Credit Suisse. As such, Pfizer Inc. is headed slightly higher in electronic trading, hoping to build on its 12.6% year-to-date advance, as of yesterday's close at $35.06. The options crowd certainly is expecting more upside from the drugmaker. At the ISE, CBOE, and PHLX, PFE has racked up a 10-day call/put volume ratio of 5.36 -- which ranks in the 84th percentile of its annual range. In other words, traders have been buying to open calls over puts at an accelerated clip of late.