骑士助手5.3:genetically modified t cells potential therap...

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August 10, 2011 — Although the data are preliminary, a novel technique shows promise as a potent and sustained method of cancer immunotherapy. Autologous T cells expressing an anti-CD19 chimeric antigen receptor (CART19) produced a rapid and long-lasting response in patients with refractory chronic lymphocytic leukemia (CLL).

In a case report published online August 10 in the New England Journal of Medicine, a patient with advanced P53-deficient CLL received a CART19 cell infusion, and on day 23, there was no evidence of CLL in the bone marrow.

Computed tomography (CT) scans performed 3 months after the procedure showed sustained remission, and bone marrow studies at 3 and 6 months showed no evidence of CLL. "The patient remains in remission 1 year after his infusions," explained first author David L. Porter, MD, professor of medicine and director of blood and marrow transplantation at the Hospital of the University of Pennsylvania, Philadelphia.

"He is fully recovered from any and all side effects, has no symptoms, and is fully functional," he told Medscape Medical News.

A second patient who experienced a complete response after CART19 infusions also remains in remission 1 year after therapy. "The third patient had a dramatic but partial response," said Dr. Porter. "He has relatively stable disease."

Gene transfer techniques have been developed to genetically modify T cells to stably express antibodies on their surface, conferring new antigen specificity, note the authors. Chimeric antigen receptors combine an antigen-recognition domain of a specific antibody with an intracellular domain of the CD3-zeta chain or FcγRI protein into a single chimeric protein. The authors report that including the CD137 (4-1BB) signaling domain in preclinical models significantly increased antitumor activity, along with "in vivo persistence of chimeric antigen receptors," compared with the CD3-zeta chain alone.

The authors point out that in the majority of malignancies, tumor-specific antigens are not well defined. However, that is not the case in B cell cancers, in which CD19 is a potential target, because the expression of CD19 is restricted to normal and malignant B cells and their precursors.

Even though this study is preliminary, it has tremendous potential for patients with CLL, non-Hodgkin's lymphoma, and possibly lymphoblastic leukemia (ALL), explained Dr. Porter.

"All express CD19," he said. "The only curative therapy for patients with CLL has been allogeneic SCT [stem cell transplantation], at the expense of extensive morbidity and mortality. If this therapy is effective long-term, it would have the potential to replace the need for allogeneic SCT."

"In addition, many patients are too old, have other medical problems, or don't have a suitable donor, all making allogeneic SCT impractical," he added. "Furthermore, these results show that this technology can be tremendously potent, which has broad implications for other diseases. Similar vectors can be designed to target other molecules on other tumor types."

Dr. Porter and his colleagues are planning to continue this trial in a small number of patients to better assess initial and long-term responses and toxicity. "We hope to study this therapy earlier in the course of the disease, potentially making it safer and even more effective," he said. "We plan to extend these studies to patients with other CD19-expressing malignancies, such as non-Hodgkin's lymphoma and ALL. In addition, with this powerful example of 'proof of principle,' we hope to apply this technology to patients with other malignancies."

Needs Widespread Use

In an accompanying editorial, Walter J. Urba, MD, PhD, and Dan L. Longo, MD, note that the "expansion, persistence, and development of the memory phenotype, not to mention antitumor effects, of these T cells were impressive."

Dr. Urba, from the Providence Cancer Center in Portland, Oregon, and Dr. Longo, a deputy editor at the New England Journal of Medicine, caution that toxicity could become more of a problem as more potent second- and third-generation chimeric antigen receptors are used in patients with varying tumor types. Safety measures include infusing a lower number of T cells, using immunosuppressive agents, and the "introduction of a 'suicide signal' to kill cells when they are creating mischief."

"Only with more widespread clinical use of chimeric antigen-receptor T cells will we learn whether the results reported by Porter et al. reflect an authentic advance toward a clinically applicable and effective therapy or yet another promising lead that runs into a barrier that cannot be easily overcome," they conclude.

Case Study

In this pilot study, the authors treated 3 patients with advanced CLL with autologous T cells expressing CART19, and reported on the immunologic and clinical efficacy in 1 patient.

That patient was diagnosed with stage I CLL in 1996, and first required treatment 6 years later. He was treated with rituximab plus fludarabine in 2002, which resulted in normalization of his blood counts and partial regression of his adenopathy. The patient received further treatment in 2006, and was disease-free for 20 months.

In February 2009, the patient experienced rapidly progressive leukocytosis and recurrent adenopathy, and CLL was observed in his bone marrow. Cytogenetic testing revealed a deletion of chromosome 17p in 3 of 15 cells, and fluorescence in situ hybridization (FISH) testing showed that 170 of 200 cells had a deletion involving TP53 on chromosome 17p. Patients with TP53 deletions tend to have short remissions after standard therapies, the authors note.

Autologous T cells were collected from the patient in December 2009 and cryopreserved. He then received alemtuzumab for 11 weeks. This resulted in improved hematopoiesis and partially resolved adenopathy. During the next 6 months, the patient experienced stable disease with persistent and extensive bone marrow involvement and diffuse adenopathy. In July 2010, he was enrolled in a phase 1 clinical trial of chimeric antigen-receptor-modified T cells.

Pentostatin and cyclophosphamide were administered to deplete the lymphocytes; 4 days later, the patient received 1.42 ? 10⁷ transduced T cells. The unselected T cells were infected with a self-inactivating lentiviral vector, designed by the authors to carry genes for the chimeric antigen receptor. No postinfusion cytokines were administered, and there were no toxic effects related to the infusion.

The patient began experiencing chills and a low-grade fever associated with grade 2 fatigue 14 days after the infusion. Symptoms escalated during the next 5 days, and tumor lysis syndrome was diagnosed on day 22. The patient was subsequently hospitalized, treated with fluids and rasburicase, and discharged 4 days later.

On day 28, the karyotype was normal in 15 of 15 cells, and FISH testing was negative for deletion TP53 in 198 of the 200 cells that were examined. This is considered to be within normal limits in negative control subjects, the authors note.

At 3 and 6 months after the infusion, the patient's physical exam remained unremarkable. There was no palpable adenopathy, CT scanning showed sustained remission, and bone marrow studies revealed no evidence of CLL on morphologic analysis, karyotype analysis (46,XY), or flow cytometric analysis.

N Engl J Med. Published online August 10, 2011. Abstract, Editorial

Authors and Disclosures

Journalist

Roxanne Nelson

Roxanne Nelson is a staff journalist for Medscape Oncology.