What happened

After management reported that its oral selective complement 5a receptor inhibitor, avacopan, successfully treated patients with anti-neutrophil cytoplasmic antibody-associated vasculitis (ANCA-associated vasculitis or ANCA vasculitis) in phase 3 studies, ChemoCentryx (NASDAQ:CCXI) shares jumped a blistering 278% on Tuesday at 3:30 pm EST.

So what

There are about 40,000 people in the U.S. alone with ANCA-associated vasculitis (AAV), a group of small-vessel inflammatory diseases that can damage organs, including the kidney. And there's a big need for new treatment options given that the standard of care -- chronic steroids and an immunosuppressant (such as chemotherapy) -- can lead to toxicity and life-threatening infection, as well as degraded quality of life.

A rocket soars into space.

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Fortunately, it appears ChemoCentryx has developed a better mousetrap. In phase 3 clinical trials, avacopan elicited remission in 72.3% of patients after 26 weeks, versus 70.1% of patients receiving standard care. That was good enough to achieve noninferiority. The 52-week data was even better. Remission was sustained for 65.7% of patients versus 54.9% of patients receiving standard care, a statistically significant outperformance.

Avacopan also shined in terms of safety. It delivered a significant reduction in glucocorticoid-related toxicity, an improvement in kidney function within patients with kidney disease, and improvements in quality-of-life metrics.

Now what

The positive phase 3 trial sets the stage for an FDA filing for approval in 2020. If regulators give avacopan a green light, the size of the addressable market suggests it could be a top seller, generating hundreds of millions in annual sales, depending on pricing. The positive trial also increases optimism that other studies evaluating avacopan in additional indications could also pan out. According to ChemoCentryx, existing trials address 300,000 Americans.

We'll get our next peek at avacopan's efficacy in 2020, when management expects to unveil results from two trials enrolling patients with C3G and hidradenitis suppurativa (HS), kidney diseases with a combined prevalence of more than 100,000 Americans.