A large real world analysis of the first approved treatment for a genetic form of ALS has confirmed known side effects and identified new potential risks, including a rare but serious lung condition that requires further investigation. The study, based on hundreds of reports from a U.S. safety database, offers the most detailed look yet at how Qalsody (tofersen) performs outside of clinical trials.
Researchers analyzed 409 adverse event reports submitted to the FDA for patients with amyotrophic lateral sclerosis, or ALS, who were taking Qalsody. The drug is designed to lower levels of a toxic protein caused by mutations in the SOD1 gene, which account for up to 20 percent of inherited ALS cases and about 2 percent of sporadic cases. Because the therapy must be injected directly into the spinal canal, many of the strongest safety signals were linked to the procedure itself. These included complications from spinal taps, abnormal cerebrospinal fluid findings, and neurological events such as increased pressure around the brain and inflammation of the spinal cord or brain lining.
The analysis also flagged a possible new signal for pulmonary embolism, a blockage in an artery of the lung, based on seven reports. This condition is not currently listed on the drug’s label. Respiratory disorders appeared in 63 reports overall, or about 15 percent of cases. The researchers noted that these findings “suggest a potential thromboembolic risk in specific patient populations” but stressed that the connection to Qalsody remains uncertain and requires larger studies. The median time for an adverse event to appear was about three months, though more than a fifth of reports described problems arising after a year of treatment, underscoring the need for long term monitoring.
What the Findings Mean for Patients and Doctors
Most reports came from the United States, and consumers submitted nearly half of them, followed by physicians. The data confirmed known serious side effects already listed on the label, including aseptic meningitis, myelitis, and vision changes due to optic nerve swelling. The authors emphasized that their work “provides real world evidence to inform the balance between the therapeutic potential and safety profile” of Qalsody. They called for future clinical strategies to focus on reducing both central nervous system and procedure related complications.
Looking ahead, the findings highlight the importance of continued safety surveillance as more patients receive Qalsody outside of clinical trials. The drug received accelerated approval in the U.S. based on its ability to lower a key biomarker of nerve damage, with full approval contingent on proof of clinical benefit. Researchers say the newly identified signals, particularly the potential clotting risk, deserve close attention in future studies. For now, the analysis offers clinicians a clearer roadmap for monitoring patients on this groundbreaking therapy while scientists work to confirm its long term safety and effectiveness.