Shares of Pinterest Inc. /zigman2/quotes/211319641/composite PINS -0.25% have had a strong week, rising 17% over the past three trading sessions, and the rally looks poised to continue after an upgrade to overweight from equal weight by Wells Fargo analyst Brian Fitzgerald. The stock is up more than 4% in premarket trading Friday. "Shares have materially underperformed the broader market since the company's April 2019 IPO, despite our view that the company's fundamentals remain on solid footing, as Pinterest has delivered generally solid results, handily exceeding pre-IPO targets with healthy audience and engagement growth, strong revenue growth and solid progress toward profitability," he wrote. He sees several catalysts down the road, including greater engagement stemming from more video on the platform, improvements in monetization on the heels of ad-tech upgrades, and better international monetization as the company invests in an overseas sales force. Fitzgerald said that Pinterest's average revenue per user in the U.S. was 22.5 times what it was internationally in the third quarter, compared to 3.6 times for Snap Inc. /zigman2/quotes/205087158/composite SNAP -1.63% , 4.6 times for Twitter Inc. /zigman2/quotes/203180645/composite TWTR +0.72% , and 6.9 times for Facebook Inc. /zigman2/quotes/205064656/composite FB -1.34% . He upped his price target to $30 from $28. Pinterest shares have risen 26% over the past month, but they're off 12% over three months. The S&P 500 /zigman2/quotes/210599714/realtime SPX -0.38% has climbed 4% over one month and 11% over three.