In biotechnology, stocks sometimes get a bit too far in front of themselves. When that happens, shares can take a big dip; so we asked three Motley Fool experts to weigh in on which stocks they think have climbed too much, too quickly.

Cheryl Swanson: On the back of steady gains in cancer survival rates, we've been seeing a virtual explosion in research aimed at exploiting the human body's own ability to overcome tumors. CAR-T drug developer Kite Pharma (NASDAQ:KITE) is one of the super-hot players in that area, as evidenced by the stock soaring almost 50% on the first day of trading, starting from its IPO price of $17 a share.

Has this high-flyer become too big for its own good? The stock reached its 52-week high of $89 in early January, only to slide to $60 a share -- where it now stands. The trouble with Kite Pharma is that there's a staggering amount of CAR-T companies in this footrace, and not enough difference between them.

Early-stage valuation of small, dedicated biotechs is tricky, but competition is something you simply can't ignore. Engineered T-cell drugs have shown unprecedented success in early-stage studies, ranging from 70%-90% remission rates. It's likely the eventual market will be massive, but the piece each participant gets is going to be much smaller.

Kite has to share this pie with many other companies, and it's not the leading contender by a long shot. Novartis (NYSE:NVS) is the big Kahuna in CAR-T. The big pharma's lead candidate displayed an astonishing 90% remission in children suffering from very advanced cases of treatment-resistant leukemia. By contrast, Kite's lead candidate showed a 70% response rate in a similar early-stage trial.

Kite's executives used the JP Morgan Healthcare Conference to discuss pricing of around $150,000 for one of its drugs that hasn't even begun pivotal clinical trials. I'd call that putting the "CAR-T" before the horse, and another indication this company could be getting ahead of itself. This stock is performing badly right now, and even with plenty of profit-taking potential still on the table, I'd be extra careful with this one.

Brian Orelli: If you thought Cheryl's Kite Pharma was expensive with a $2.8 billion market cap, look at Juno Therapeutics (NASDAQ:JUNO); its market cap is a staggering $4 billion.

With a market cap that large, you'd expect the company to have a drug in phase 3 development, or at least a couple in phase 2 trials. But Juno's most advanced drug is still in phase 1 trials. Granted, Juno has six of them, which it expects to increase to 10 therapeutic candidates in the clinic by the end of the year, but there's still quite a bit of risk built in with such an early-stage pipeline.

Don't get me wrong... I like Juno's -- and Kite's, for that matter -- CAR-T technology. Training the immune system to fight cancer is a very attractive idea, and CAR-T appears to work really well in the few patients it has been tested on.

But the same thing could be said for gene therapy, antisense, and RNAi. Each of those promising new technologies faced major obstacles that required years to work out. Even antibody drugs, where we've reached a stage that they fail because of a bad target not because of the underlying technology, took decades to develop.

I wouldn't suggest shorting companies working on the technology; it's certainly possible the CAR-T therapies zoom through clinical development and don't get hung up on unforeseen problems. But I also wouldn't suggest making oversized investments in them. I'm not convinced the risk is fully priced into their valuations.

Leo Sun: Pharmacyclics (UNKNOWN:PCYC.DL), the maker of the blood-disorder drug Imbruvica, rallied 33% since the beginning of the year to all-time highs, but now trades at a pricey 146 times trailing earnings.

Imbruvica, which is Pharmacyclics' only approved drug, is co-marketed with Johnson & Johnson (NYSE:JNJ), with which it splits profits evenly. The drug has been approved for three blood disorders so far: mantle cell lymphoma (MCL), chronic lymphocytic leukemia (CLL), and Waldenstrom's macroglobulinemia. Based on those approvals and future potential indications, Imbruvica is expected to generate peak sales between $4 billion and $9 billion.

While keeping half of that would be great news for the company, it's nowhere close to hitting those numbers yet. For fiscal 2014, Pharmacyclics expects Imbruvica to generate U.S. net-product revenue of $492 million. During the fourth quarter, U.S. revenue is expected to rise 31% sequentially to approximately $185 million. That's only a moderate improvement from the 29% sequential growth it reported in the previous quarter.

Although Pharmacyclics is testing Imbruvica on additional indications and working on overseas approvals, there are also concerns regarding pricing and competition. Imbruvica's $130,000 per-year wholesale price could leave it vulnerable to potential competitors like Gilead Sciences' Zydelig and AbbVie's ABT-199.

In the long run, Pharmacyclics might become the next Celgene. But for the now, the stock is a very pricey one dependent on a narrow pipeline.