Cell therapy KYV-101 eases symptoms in small trial for hard-to-treat gMG

Kyverna Therapeutics’ experimental cell therapy KYV-101, now called mivocabtagene autoleucel (miv-cel), was associated with rapid, sustained symptom improvements in all seven participants with hard-to-treat generalized myasthenia gravis (gMG) in a clinical trial.

The data specifically show that all seven treated to date with miv-cel in the Phase 2 portion of the Phase 2/3 KYSA-6 trial (NCT06193889) had clinically meaningful reductions in two measures of disease severity: the MG Activities of Daily Living (MG-ADL) and the Quantitative MG (QMG).

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The findings were recently shared in an oral presentation, titled “Update on the Phase Two Portion of KYSA-6, an Open-label, Single-arm, Multicenter Study of KYV-101, a Fully Human CD19 Chimeric Antigen Receptor (CAR) T-cell Therapy in Generalized Myasthenia Gravis (gMG),” at the American Academy of Neurology Annual Meeting, held April 18-22 in Chicago and virtually.

“We are pleased to share updated data for miv-cel that continue to demonstrate the depth and durability of response across key outcome measures in patients with generalized myasthenia gravis, setting a new clinical standard,” Warner Biddle, CEO of Kyverna, said in a company press release. “Our data reinforces confidence in miv-cel’s differentiated profile [and] strengthens our conviction in the ongoing Phase 3 trial.”

In the study’s ongoing Phase 3 portion, participants are being randomly assigned to receive either miv-cel or standard-of-care MG therapies, with the main goals of determining whether the experimental cell therapy is better than standard treatment at improving MG-ADL and/or QMG scores. Adults with hard-to-manage gMG are currently being recruited at sites in the U.S., Australia, Brazil, and Germany.

“The ability of miv-cel to achieve minimal symptom expression while eliminating the need for chronic immunotherapies following a single dose represents a meaningful clinical advancement with the potential to significantly improve daily function and quality of life for patients,” said Srikanth Muppidi, MD, investigator in the KYSA-6 trial at Stanford Medicine. “I’m encouraged by these findings and look forward to the results from the Company’s Phase 3 trial.”

How CAR T-cell therapy targets the disease in gMG

In gMG, self-targeting antibodies interfere with communication between nerve and muscle cells, leading to symptoms such as fatigue and muscle weakness.

Miv-cel aims to deplete B-cells, the immune cells that produce MG-causing antibodies. In doing so, the therapy is designed to lower levels of these antibodies and potentially ease symptoms.

A CAR T-cell therapy, miv-cel involves collecting T-cells (another type of immune cell) from a patient, then engineering them with a human-made receptor that directs them to target B-cells.

Patients undergo a round of chemotherapy to reduce existing immune cells and make room for the therapy, after which the modified T-cells are infused back into the patient to target B-cells.

The KYSA-6 trial is specifically testing the therapy in gMG patients positive for the two most common types of MG-related antibodies, those targeting acetylcholine receptor (AChR) and muscle-specific kinase (MuSK). Participants have persistent gMG symptoms despite prior treatment with available therapies.

Newly presented data covered the seven participants in the study’s Phase 2 portion who received a single dose of miv-cel as of late February, at which point all had been followed for at least three months, with a few followed for more than a year.

Kyverna reported that all treated patients experienced at least a three-point drop in both MG-ADL and QMG scores, a reduction that is considered clinically significant. Available data showed that, at about six months after miv-cel treatment, the average score reduction was 8.5 points for MG-ADL and 11.3 points for QMG.

Additional measure shows consistent symptom improvement

Another measure of disease severity called the Myasthenia Gravis Composite (MGC) showed similar trends: all seven patients experienced clinically meaningful improvements, with an average score drop of 16 points.

At last follow-up, more than half of the patients (57%) had achieved minimal symptom expression, corresponding to an MG-ADL score of 0 or 1 and reflecting no or minimal impact of the disease on daily life.

Kyverna noted that deep reductions in these disease severity scores were seen within two weeks of miv-cel treatment. Among the three patients with longer follow-up, responses were sustained for up to one year. The company also reported that patients remained free of nonsteroidal immunosuppressants, high-dose steroids, and FcRn or complement inhibitors through about six months.

Miv-cel was generally tolerated well. As previously reported, a few of the participants experienced severe low levels of neutrophils, a type of immune cell, which is a common and expected side effect of the chemotherapy used to prepare for treatment. No other serious safety issues were documented.

“Notably, today’s longer-term data demonstrate the continued deepening of response over time across multiple clinical outcome measures,” said Naji Gehchan, MD, Kyverna’s chief medical and development officer. “These profound and unprecedented results are driven by miv-cel’s unique ability to target the disease at the source, deeply depleting B-cells to drive an immune reset and achieve durable drug-free, disease-free remission for patients with generalized myasthenia gravis.”