Neuroblastoma, a rare pediatric cancer, has no FDA-approved treatments for patients who relapse after the first line of therapies. Y-mAbs Therapeutics has developed two experimental antibody drugs for the disease and it is lining now lining up an IPO to as it readies both therapies for submission to the FDA for approval.
Y-mAbs set a preliminary $92 million target for its IPO, filed Friday. The New York-based company plans to list its shares on the Nasdaq under the stock symbol “YMAB.”
Neuroblastoma is a rare cancer affecting children that starts in the early development of nerve cells. The first Y-mAbs drug, naxitamab, targets a molecule on the surface of tumors called GD2. While there are other approved antibody therapies that target GD2, Y-mAbs says its drug has advantages compared to those treatments. Naxitamab has been shown to be less toxic in studies, which allows for stronger doses and shorter infusion times of the drug, Y-mAbs says in its prospectus. Unlike currently available GD2 drugs that require infusions lasting between 10 to 20 hours and days of hospitalization, the Y-mAbs drug can be given in roughly 30 minutes on an outpatient basis. The company adds that no life-threatening side effects have been observed in patients treated with its drug.
Y-mAbs is testing naxitamab in a Phase 2 study expected to enroll 37 patients. The company says that the data from this study, combined with an earlier dose-escalation study, will form the basis of its FDA submission. In the 23 patients enrolled in the dose-escalation study, the overall response rate, a measure of the reduction of the cancer, was 57 percent. Based on its discussions with the FDA, Y-mAbs says it expects that the drug could qualify for accelerated approval if its studies show an overall response rate of 30 percent.
Tests of naxitamab are resuming following a partial clinical hold on the study, which was issued last October. According to Y-mAbs, the FDA states that that the parameters of tests used to assess toxicity were too wide. After responding and meeting with the FDA, the partial hold on the Y-mAbs drug was lifted in June.
Y-mAbs says that while the current focus for naxitamab is rare pediatric cancers, the drug’s use could later be expanded to adults whose cancers express GD2. The company estimates that 200,000 adult patients were newly diagnosed with such cancers in the United States last year.
The second Y-mAbs drug, omburtamab, is radiolabeled, meaning it has small radioactive particles attached to the antibodies. The drug targets a protein called B7-H3. It’s is an experimental treatment for a central nervous system complication of neuroblastoma called leptomeningeal metastases, in which the cancer spreads to the membranes surrounding the brain and the spinal cord. In a Phase 1 study, the median overall survival of the 93 patients treated with omburtamab was 47 months, according to the securities filing. By comparison, the historical median overall survival of patients who have the complication is approximately six months. The drug is also in early-stage testing in two other rare pediatric cancers.
Y-mAbs says it will use the IPO proceeds to complete clinical testing of its two lead neuroblastoma drugs, which the company expects will be ready for submission to the FDA for review sometime next year. The cash will also support further development of other compounds in preclinical development.
Other companies are also pursuing drugs that go after the same targets as the Y-mAbs drugs. MacroGenics and Daiichi Sankyo are both developing drugs that target B7-H3, Y-mAbs says in its filing. United Therapeutics (NASDAQ: UTHR) received the FDA nod in 2015 for its GD2 antibody drug dinutuximab (Unituxin). The drug was approved to treat high-risk neuroblastoma in patients who have shown a partial response to first-line treatments for the disease.
Y-mAbs, founded in 2015, is led by CEO Claus Juan Møller San Pedro, who was a co-founder of Danish biotech Genmab. The Y-mAbs cancer drugs were licensed from Memorial Sloan Kettering Cancer Center in New York, which stands to gain milestone payments as the drugs progress, and royalties from sales if any of them are approved.
Both Y-mAbs and Memorial Sloan Kettering could also see another financial windfall. Naxitamab and omburtamab have both received rare pediatric disease designation from the FDA, which qualifies Y-mAbs to receive priority review vouchers if the drugs are approved. Companies can apply these vouchers to speed up the review of another rare disease drug. The FDA meant for these vouchers to help incentivize development of new treatments for rare diseases, but they have become also valuable commodities themselves, bought and sold at prices topping $100 million. According to the Y-mAbs filing, Memorial Sloan Kettering is entitled to receive up to half of the proceeds generated from selling the first priority review voucher, and 33 percent from the sale of any subsequent vouchers.
Y-mAbs has raised more than $89 million from equity investments, according to the filing, most recently a $50 million financing last October. The largest Y-mAbs shareholder is WG Biotech, which currently owns a 17.83 percent stake in the company, according to the filing. Memorial Sloan Kettering is the second-largest shareholder, owning 9.79 percent of the company; IBM Healthcare owns 8.85 percent. Y-mAbs’s balance sheet shows $70.1 million in cash as of June 30. In the first half of 2018, the company spent $14.4 million on research and development, eclipsing its entire R&D total for all of last year.
Neuroblastoma image by the National Cancer Institute