Biotech stocks are known for dramatic gains, and this year's top performers are helping the industry live up to its reputation. Investors excited about the future of gene therapy have seen CRISPR Therapeutics AG (NASDAQ:CRSP) more than quadruple its shareholders' money over the past year.

The gene-editing stock has put up a dazzling performance, but it pales in comparison to Endocyte Inc. (NASDAQ:MRNS) and Arrowhead Pharmaceuticals Inc. (NASDAQ:ARWR), which have absolutely exploded lately. Let's look at what's next for these high-flying biotech stocks to see if any have a shot at climbing further.

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1. Endocyte Inc.: Waiting for a Vision 

Shares of this precommercial biotech have risen a spectacular 807% over the past year as investors become increasingly confident about its new lead candidate's chances. The radioactive cancer treatment called Lu-PSMA-617 recently began a pivotal trial called Vision that will test its ability to increase overall survival for prostate cancer patients that have run out of treatment options.

The Vision study will enroll up to 750 patients who have progressed following treatment with standard chemo and either Xtandi or Zytiga. Endocyte is currently running a mid-stage study that enrolled 50 patients that keeps throwing off encouraging data. Overall survival among the first 30 patients treated with Lu-PSMA-617 was 13.5 months, which is significantly higher than oncologists would expect from this population.

If Endocyte's candidate hits the mark in the Vision study, this stock could soar further, but there's a slight chance that investors might not have to wait that long. Oncologists measure prostate-specific antigen (PSA) levels to gauge disease activity, and Lu-PSMA-617 has shown a breathtaking ability to lower circulating PSA. Just two of 50 people treated with the candidate exhibited a higher score and 62% lowered their scores by more than half. The company would like to apply for an accelerated approval based on Lu-PSMA-617's ability to lower circulating PSA, which won't take nearly as long to prove as an overall survival benefit. The agency has been increasingly willing to bend the rules in order to speed up development of potentially life-saving drugs, so it's probably worth keeping your fingers crossed.

2. Arrowhead Pharmaceuticals: Flurry of activity ahead

Multiple shots on goal helped this biotech stock explode 768% higher over the past year. In March, Arrowhead dosed the first patient with one of its RNA interference drugs, ARO-AAT for the treatment of rare liver disease. In May, it began its second human study with a hepatitis B candidate called ARO-HBV. A cardiovascular candidate partnered with Amgen could be next, and applications to begin studies in Europe for three more candidates are scheduled for submission by year's end. 

Arrowhead's experimental drugs work by limiting the expression of troublesome genes. I'm fairly confident ARO-AAT will limit production of the proteins associated with alpha-1 antitrypsin deficiency, but whether that will translate into a measurable benefit is still anybody's guess.

The company expects to present early trial data for ARO-AAT and its hepatitis B candidate, ARO-HBV, at a scientific conference this November. Early signs of efficacy, without any safety issues, could allow the stock to continue climbing.

3. CRISPR Therapeutics AG: Plenty of potential

While Arrowhead intends to silence trouble making genes, this biotech is developing new drug candidates that can disrupt, delete, and even correct them. The World Health Organization estimates 10,000 diseases are caused by problems with a single gene, and investors hoping CRISPR Therapeutics can develop drugs to treat at least a handful of these targets have driven the stock 315% higher over the past year.

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Recent findings from independent laboratories suggest treatments that correct genes might be more difficult than expected, but CRISPR's most advanced experimental treatments are the sort that disrupt genes. One of those disruptive therapies, CTX001, has been cleared to start a clinical study in Europe, and the first of perhaps 30 beta-thalassemia patients will receive a dose later this year.

Beta-thalassemia patients can't produce enough hemoglobin on their own and rely on frequent blood transfusions. If CRISPR Therapeutics can show that CTX101 safely and effectively helps these patients produce enough functional hemoglobin to break free of transfusion dependency, the stock could jump.

The thing about big expectations

CRISPR Therapeutics investors are already expecting tremendous results from the first human study with one of its drugs. The company's market cap has swelled to around $2.9 billion at recent prices. That's an awful lot for a company roughly a year away from producing its first human proof-of-concept data. If the results aren't spectacular, the stock could tumble.

The same could be said of Arrowhead and its recent $1.2 billion market cap. Although RNA interference drugs have already proven themselves in a clinical setting, we haven't seen human data from anything this company's discovered yet. With expectations so high, there's a lot to lose if early results are less than tremendous.

Surprisingly, the only stock here with clinical data has the lowest valuation. Its recent market cap of $983 million could get squeezed if PSA scores don't translate into survival benefits, but that seems like a relatively safe bet these days.

Cory Renauer has no position in any of the stocks mentioned. The Motley Fool owns shares of CRISPR Therapeutics. The Motley Fool has a disclosure policy.