Repligen trades at $124.97 and has moved in lockstep with the market. Its shares have returned 7.6% over the last six months while the S&P 500 has gained 6.6%.

Is now the time to buy Repligen, or should you be careful about including it in your portfolio? See what our analysts have to say in our full research report, it’s free.

Why Do We Think Repligen Will Underperform?

We're cautious about Repligen. Here are three reasons why RGEN doesn't excite us and a stock we'd rather own.

1. Fewer Distribution Channels Limit its Ceiling

Larger companies benefit from economies of scale, where fixed costs like infrastructure, technology, and administration are spread over a higher volume of goods or services, reducing the cost per unit. Scale can also lead to bargaining power with suppliers, greater brand recognition, and more investment firepower. A virtuous cycle can ensue if a scaled company plays its cards right.

With just $738.3 million in revenue over the past 12 months, Repligen is a small company in an industry where scale matters. This makes it difficult to build trust with customers because healthcare is heavily regulated, complex, and resource-intensive.

2. Shrinking Adjusted Operating Margin

Adjusted operating margin is one of the best measures of profitability because it tells us how much money a company takes home after subtracting all core expenses, like marketing and R&D. It also removes various one-time costs to paint a better picture of normalized profits.

Looking at the trend in its profitability, Repligen’s adjusted operating margin decreased by 18.3 percentage points over the last five years. This raises questions about the company’s expense base because its revenue growth should have given it leverage on its fixed costs, resulting in better economies of scale and profitability. Its adjusted operating margin for the trailing 12 months was 13.8%.

3. New Investments Fail to Bear Fruit as ROIC Declines

We like to invest in businesses with high returns, but the trend in a company’s ROIC is what often surprises the market and moves the stock price. Unfortunately, Repligen’s ROIC has decreased significantly over the last few years. Paired with its already low returns, these declines suggest its profitable growth opportunities are few and far between.

Final Judgment

We cheer for all companies helping people live better, but in the case of Repligen, we’ll be cheering from the sidelines. That said, the stock currently trades at 65.6× forward P/E (or $124.97 per share). This valuation tells us a lot of optimism is priced in - we think other companies feature superior fundamentals at the moment. We’d recommend looking at a safe-and-steady industrials business benefiting from an upgrade cycle.

Stocks We Would Buy Instead of Repligen

ONE MORE THING: Top 5 Growth Stocks. The biggest stock winners almost always had one thing in common before they ran. Revenue growing like crazy. Meta. CrowdStrike. Broadcom. Our AI flagged all three. They returned 315%, 314%, and 455%, respectively.

Find out which 5 stocks it's flagging for this month — FREE. Get Our Top 5 Growth Stocks for Free HERE.

Stocks that have made our list include now familiar names such as Nvidia (+1,326% between June 2020 and June 2025) as well as under-the-radar businesses like the once-micro-cap company Kadant (+351% five-year return). Find your next big winner with StockStory today.