While CFTR modulators have stolen the cystic fibrosis treatment spotlight, Corbus Pharmaceuticals has quietly tackled CF’s inflammatory and fibrotic components. Resunab, Corbus’s investigative agent, has the potential to achieve first-in-class status.

Clinching both orphan-drug and fast-track FDA designations, Resunab could prolong survival for CF patients in combination with CFTR modulators or as a stand-alone therapy. Unlike CFTR modulators designed to address the underlying cause of CF, however, Corbus has positioned Resunab to reduce inflammation. Corbus recently initiated a Phase II clinical study supported by a $5 million award from Cystic Fibrosis Foundation Therapeutics. The study will enroll about 70 adults with CF regardless of their CFTR mutation.

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In patients with CF, the abnormal transport of chloride and sodium ions across the pulmonary epithelium causes thick mucus to accumulate in the lungs. The abnormal function results in chronic inflammation, leading to a cascade of issues — from persistent bacterial infection to excessive airway inflammation and fibrosis.

Current treatments, including steroids and ibuprofen, help control symptoms. But the side-effect profiles are difficult for patients to manage. “And steroids are not a good long-term option for children,” notes Liisa Bayko, an analyst with JMP Securities.

“The immune system is constantly on, which is tremendously destructive.”

-Yuval Cohen, CEO of Corbus Pharmaceuticals

Yuval Cohen, CEO of Corbus, explains that many patients with CF take 1,000 mg to 3,000 mg of ibuprofen daily for anti-inflammatory purposes. “The anti-inflammatories stop the pro-inflammatory cascade, leading to immunosuppression — which is unacceptable for these patients,” he says. “Resunab focuses on the off switch and returns the immune response to normal.”

The promise Resunab potentially holds is twofold, Cohen adds. “First, we don’t take inflammation down to zero, but rather restore it to normal. That’s an attractive safety profile for this disease,” he explains. “And second, all CF patients have chronic damaging inflammation and could benefit from a therapy like Resunab.”

CF has a devastating effect on the immune system almost from birth, he says. “The immune system is constantly on, which is tremendously destructive.”

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A bit ahead of Corbus on the development curve, Celtaxsys’s CTX-4430 aims to target the overactivated inflammation response. Bayko suggests that CTX-4430 and Resunab could be used together. “The agents could be complementary,” she explains. “And the companies, while competitors, could be friendly competitors.”

Bayko anticipates that Resunab’s Phase II data will be released by year end. “It’s an early study looking for preliminary biomarker changes,” she adds. “If we know the drug is working on target, then it should be a de-risking event for the stocks. Either way, the data should be an important catalyst.”