CAR T-cell therapy shows sustained benefits in three gMG patients

The investigational CAR T-cell therapy KYV-101, or mivocabtagene autoleucel (miv-cel), improves muscle strength and daily functioning in people with hard-to-treat generalized myasthenia gravis (gMG), with benefits lasting for up to two years after dosing.

That’s according to data from three patients with self-reactive antibodies against acetylcholine receptors (AChR), the most common gMG-driving antibody, who were treated with miv-cel outside of clinical trials. All were also able to discontinue gMG-specific immunotherapies within the first weeks after miv-cel treatment.

“Our findings support the notion that [this type of] CAR T cell therapy may represent a promising treatment approach for selected patients with [self-reactive antibodies], [treatment-resistant] gMG, with an acceptable safety profile and long-term remission,” researchers wrote.

The case series was described in the study “Long-term outcomes of anti-CD19 CAR T cell therapy in refractory myasthenia gravis: A case series,” which was published in Cell Reports Medicine. It was conducted by researchers in Germany and employees of the therapy’s developer, Kyverna Therapeutics, which also provided financial support.

These results add to those reported from the seven people with hard-to-treat gMG who received the treatment in the Phase 2 portion of the Phase 2/3 KYSA-6 clinical trial (NCT06193889). These patients showed rapid, sustained clinically meaningful reductions in disease severity, with more than half showing no or minimal disease impact on daily life.

In the ongoing Phase 3 portion, up to 66 adults with treatment-resistant gMG are being recruited at 22 sites worldwide. All must test positive for one of the two most common types of gMG-related antibodies, those targeting AChR and those targeting the muscle-specific kinase protein.

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Miv-cel targets B-cells

In gMG, the immune system mistakenly attacks proteins needed for nerve-muscle communication, leading to symptoms such as muscle weakness and fatigue.

Miv-cel is a CAR T-cell therapy designed to target and eliminate B-cells, the immune cells that produce antibodies, including those that drive gMG. It involves the collection of immune T-cells (which can kill other cells) from the patient and their modification in the lab to carry a chimeric antigen receptor (CAR) protein that binds to CD19, a protein on the surface of B-cells.

The engineered T-cells are then infused back into the patient to promote the death of CD19-positive B-cells, which is expected to lower levels of self-reactive antibodies and ease disease severity.

In this study, researchers presented two-year data from two women and one man with hard-to-treat gMG and who tested positive for anti-AChR antibodies. All three had persistent symptoms despite treatment with corticosteroids and at least two additional immunosuppressive therapies.

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All three patients achieved disease remission

The first case involved a 33-year-old woman who was living with gMG for 11 years. She experienced worsening function of the swallowing, chewing, and breathing muscles in recent years, including five myasthenic crises (severe breathing problems that require hospitalization).

After receiving miv-cel, her condition improved rapidly. The quantitative myasthenia gravis score, a measure of muscle weakness, decreased from 15 to two after about four months, indicating a state of near remission. Her score on the Myasthenia Gravis Activities of Daily Living scale, which assesses the disease’s impact on daily activities, dropped (improved) to zero within one week.

The woman’s ability to walk also improved significantly. Her anti-AChR antibody levels initially fell substantially, but then stabilized at relatively low levels.

The second patient, a 76-year-old man, had three myasthenic crises within the first 10 months after his diagnosis and developed severe swallowing problems requiring a feeding tube.

The man experienced gradual improvements over several months after receiving miv-cel. His feeding tube was removed three months after treatment, and he regained the ability to walk normally after nearly seven months and was later able to go on mountain hikes. Also, his anti-AChR antibody levels fell by about 10 times, “consistent with an expected antibody-associated response pattern,” the researchers wrote.

These data support anti-CD19 CAR T cell therapy as a durable, effective intervention for [hard-to-treat gMG] and warrant further evaluation in prospective controlled clinical trials.

The third patient was a 37-year-old woman who was living with the disease for 10 years. Before receiving miv-cel, her symptoms worsened between treatment administrations and she had recurrent mild-to-moderate infections. She had also developed another autoimmune disease, rheumatoid arthritis.

After miv-cel, the woman experienced a rapid improvement, regaining full walking ability after one month. However, her anti-AChR antibody levels (which were lower than in the other two cases) remained largely unchanged.

At last follow-up (two years in the first case and about 1.5 years in the other two), all three patients were in disease remission without any gMG-specific treatment, which was discontinued in the first weeks after miv-cel treatment.

Miv-cel was generally well tolerated. None of the women experienced serious adverse events. The man developed mild cytokine release syndrome, an immune reaction that can occur after CAR T-cell therapy, and severely low levels of a type of immune cell called neutrophils, which resolved with treatment. Infections were uncommon and mild.

“These data support anti-CD19 CAR T cell therapy as a durable, effective intervention for [hard-to-treat gMG] and warrant further evaluation in prospective controlled clinical trials,” the researchers wrote.