Unlike yesterday, when the S&P 500 (SNPINDEX:^GSPC) witnessed its worst decline in weeks on generally positive economic data, the markets were privy to less-than-impressive economic data today, yet still climbed to the upside.

Specifically, the Producer Price Index for May came in with a decline of 0.2%, which, while nice for businesses in that it demonstrates lower month-over-month pricing, is concerning because it could lead to a deflationary environment, which hurts the ability of businesses to raise prices and grow margins. I wouldn't read too much into this decline just yet, considering the rapid incline the PPI has had during the past couple of months, but it's a situation worth monitoring.

In addition, the Thomson Reuters/University of Michigan preliminary June consumer sentiment figure dipped to a reading of 81.2 from 81.9 in the previous month. A drop here signifies that consumers are less confident about their short- and long-term financial outlooks. The idea likely to spend, which could adversely impact U.S. GDP growth.

Despite these concerns, investors shook off the S&P 500's three-day losing streak, and ended the week on a high note by rising 6.05 points (0.31%), to close at 1,936.16.

Source: MyFuture.com, Flickr.

The real market leader today came from the biotech sector with Karyopharm Therapeutics (NASDAQ:KPTI) surging incessantly throughout the day, and ending higher by 93.5% after announcing phase 1 data of its investigational drug selinexor in combination with low-dose dexamethasone in heavily pretreated multiple myeloma patients. Initial results of its study demonstrated that the overall response rate was 50%, with a clinical benefit rate of 75%. What's incredible about these results is that the average patient had received 5.5 prior lines of therapy. Also, adverse events associated with the combo therapy were generally low-grade in nature, meaning it was well-tolerated.

Simply put, most patients often don't have much of an overall response in the later stages of multiple myeloma, so Karyopharm's impressive response rate is turning some heads. Keep in mind, though, that we're only talking about a handful of patients here, and we may want to reserve judgment until we have a bigger patient pool to study.

Shares of online restaurant reservation company OpenTable (UNKNOWN:UNKNOWN) exploded to the upside by 48.4%, or more than $34 per share, after Priceline Group (NASDAQ:BKNG) agreed to purchase the company, which allows restaurants to fill their tables days or weeks in advance in exchange for a fee, for $2.6 billion, or $103 per share in cash. Both boards of directors have approved the transaction, and it's expected to close in the third quarter.

Source: Dru Kelly, Flickr.

I suspect this deal, while taking Wall Street and investors by surprise, will work out well for both companies, with Priceline seeing immediately accretive benefits from its purchase, and further improving consumer convenience. For OpenTable, aside from shareholders receiving a hefty premium to yesterday's closing price, it gives the company a way of expanding overseas via Priceline's network.

Lastly, shares of struggling retailer Express (NYSE:EXPR) rallied 21.4% after confirming yesterday that it had received a letter from private-equity firm Sycamore Partners that it may make a bid for the company. Sycamore currently owns 9.9% of all outstanding shares of Express, so a bid wouldn't come as too much of a shock; however, Express' shareholder rights plan may make acquiring the company difficult if a significant (and likely unwarranted) premium isn't included.

While Brean Capital took the opportunity to push its price target on Express to $20 from $16 today, I'd suggest that investors consider taking this gift and heading for the exits. Following three consecutive earnings misses and an expected revenue decline in fiscal 2015, it's pretty evident that the company has lost touch with its customer base. Until such time as Express can demonstrate robust same-store sales growth, I suggest staying on the sidelines.