Penn Medicine News: Genetically Modified "Serial Killer" T …

(PHILADELPHIA) -- In a cancer treatment breakthrough 20 years in the making, researchers from the University of Pennsylvania's Abramson Cancer Center and Perelman School of Medicine have shown sustained remissions of up to a year among a small group of advanced chronic lymphocytic leukemia (CLL) patients treated with genetically engineered versions of their own T cells. The protocol, which involves removing patients' cells and modifying them in Penn's vaccine production facility, then infusing the new cells back into the patient's body following chemotherapy, provides a tumor-attack roadmap for the treatment of other cancers including those of the lung and ovaries and myeloma and melanoma. The findings, published simultaneously today in the New England Journal of Medicine and Science Translational Medicine, are the first demonstration of the use of gene transfer therapy to create "serial killer" T cells aimed at cancerous tumors.

"Within three weeks, the tumors had been blown away, in a way that was much more violent than we ever expected," said senior author Carl June, MD, director of Translational Research and a professor of Pathology and Laboratory Medicine in the Abramson Cancer Center, who led the work. "It worked much better than we thought it would."

The results of the pilot trial of three patients are a stark contrast to existing therapies for CLL. The patients involved in the new study had few other treatment options. The only potential curative therapy would have involved a bone marrow transplant, a procedure which requires a lengthy hospitalization and carries at least a 20 percent mortality risk -- and even then offers only about a 50 percent chance of a cure, at best.

"Most of what I do is treat patients with no other options, with a very, very risky therapy with the intent to cure them," says co-principal investigator David Porter, MD, professor of Medicine and director of Blood and Marrow Transplantation. "This approach has the potential to do the same thing, but in a safer manner."

Secret Ingredients June thinks there were several "secret ingredients" that made the difference between the lackluster results that have been seen in previous trials with modified T cells and the remarkable responses seen in the current trial. The details of the new cancer immunotherapy are detailed in Science Translational Medicine.

After removing the patients' cells, the team reprogrammed them to attack tumor cells by genetically modifying them using a lentivirus vector. The vector encodes an antibody-like protein, called a chimeric antigen receptor (CAR), which is expressed on the surface of the T cells and designed to bind to a protein called CD19.

Once the T cells start expressing the CAR, they focus all of their killing activity on cells that express CD19, which includes CLL tumor cells and normal B cells. All of the other cells in the patient that do not express CD19 are ignored by the modified T cells, which limits side effects typically experienced during standard therapies.

The team engineered a signaling molecule into the part of the CAR that resides inside the cell. When it binds to CD19, initiating the cancer-cell death, it also tells the cell to produce cytokines that trigger other T cells to multiply -- building a bigger and bigger army until all the target cells in the tumor are destroyed.

Serial Killers "We saw at least a 1000-fold increase in the number of modified T cells in each of the patients. Drugs don't do that," June says. "In addition to an extensive capacity for self-replication, the infused T cells are serial killers. On average, each infused T cell led to the killing of thousands of tumor cells and overall, destroyed at least two pounds of tumor in each patient."

The importance of the T cell self-replication is illustrated in the New England Journal of Medicine paper, which describes the response of one patient, a 64-year old man. Prior to his T cell treatment, his blood and marrow were replete with tumor cells. For the first two weeks after treatment, nothing seemed to change. Then on day 14, the patient began experiencing chills, nausea, and increasing fever, among other symptoms. Tests during that time showed an enormous increase in the number of T cells in his blood that led to a tumor lysis syndrome, which occurs when a large number of cancer cells die all at once.

By day 28, the patient had recovered from the tumor lysis syndrome and his blood and marrow showed no evidence of leukemia.

"This massive killing of tumor is a direct proof of principle of the concept," Porter says.

The Penn team pioneered the use of the HIV-derived vector in a clinical trial in 2003 in which they treated HIV patients with an antisense version of the virus. That trial demonstrated the safety of the lentiviral vector used in the present work.

The cell culture methods used in this trial reawaken T cells that have been suppressed by the leukemia and stimulate the generation of so-called "memory" T cells, which the team hopes will provide ongoing protection against recurrence. Although long-term viability of the treatment is unknown, the doctors have found evidence that months after infusion, the new cells had multiplied and were capable of continuing their seek-and-destroy mission against cancerous cells throughout the patients bodies.

Moving forward, the team plans to test the same CD19 CAR construct in patients with other types of CD19-positive tumors, including non-Hodgkin's lymphoma and acute lymphocytic leukemia. They also plan to study the approach in pediatric leukemia patients who have failed standard therapy. Additionally, the team has engineered a CAR vector that binds to mesothelin, a protein expressed on the surface of mesothelioma cancer cells, as well as on ovarian and pancreatic cancer cells.

In addition to June and Porter, co-authors on the NEJM paper include Bruce Levine, Michael Kalos, and Adam Bagg, all from Penn Medicine. Michael Kalos and Bruce Levine are co-first authors on the Science Translational Medicine paper. Other co-authors include June, Porter, Sharyn Katz and Adam Bagg from Penn and Stephan Grupp the Children's Hospital of Philadelphia.

The work was supported by the Alliance for Cancer Gene Therapy, a foundation started by Penn graduates Barbara and Edward Netter, to promote gene therapy research to treat cancer, and the Leukemia & Lymphoma Society.

The Perelman School of Medicine has been ranked among the top five medical schools in the United States for the past 17 years, according toU.S. News & World Report's survey of research-oriented medical schools. The School is consistently among the nation's top recipients of funding from the National Institutes of Health, with $392 million awarded in the 2013 fiscal year.

The University of Pennsylvania Health System's patient care facilities include: The Hospital of the University of Pennsylvania -- recognized as one of the nation's top "Honor Roll" hospitals byU.S. News & World Report; Penn Presbyterian Medical Center; Chester County Hospital; Lancaster General Health; Penn Wissahickon Hospice; and Pennsylvania Hospital -- the nation's first hospital, founded in 1751. Additional affiliated inpatient care facilities and services throughout the Philadelphia region include Chestnut Hill Hospital and Good Shepherd Penn Partners, a partnership between Good Shepherd Rehabilitation Network and Penn Medicine.

Penn Medicine is committed to improving lives and health through a variety of community-based programs and activities. In fiscal year 2013, Penn Medicine provided$814million to benefit our community.

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Penn Medicine News: Genetically Modified "Serial Killer" T ...

CAR T-Cell Immunotherapy for ALL – National Cancer Institute

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For years, the cornerstones of cancer treatment have been surgery, chemotherapy, and radiation therapy. Over the last decade, targeted therapies like imatinib (Gleevec) and trastuzumab (Herceptin)drugs that target cancer cells by homing in on specific molecular changes seen primarily in those cellshave also emerged as standard treatments for a number of cancers.

Illustration of the components of second- and third-generation chimeric antigen receptor T cells. (Adapted by permission from the American Association for Cancer Research: Lee, DW et al. The Future Is Now: Chimeric Antigen Receptors as New Targeted Therapies for Childhood Cancer. Clin Cancer Res; 2012;18(10); 278090. doi:10.1158/1078-0432.CCR-11-1920)

And now, despite years of starts and stutter steps, excitement is growing for immunotherapytherapies that harness the power of a patients immune system to combat their disease, or what some in the research community are calling the fifth pillar of cancer treatment.

One approach to immunotherapy involves engineering patients own immune cells to recognize and attack their tumors. And although this approach, called adoptive cell transfer (ACT), has been restricted to small clinical trials so far, treatments using these engineered immune cells have generated some remarkable responses in patients with advanced cancer.

For example, in several early-stage trials testing ACT in patients with advanced acute lymphoblastic leukemia (ALL) who had few if any remaining treatment options, many patients cancers have disappeared entirely. Several of these patients have remained cancer free for extended periods.

Equally promising results have been reported in several small trials involving patients with lymphoma.

These are small clinical trials, their lead investigators cautioned, and much more research is needed.

But the results from the trials performed thus far are proof of principle that we can successfully alter patients T cells so that they attack their cancer cells, said one of the trial's leaders, Renier J. Brentjens, M.D., Ph.D., of Memorial Sloan Kettering Cancer Center (MSKCC) in New York.

Adoptive cell transfer is like giving patients a living drug, continued Dr. Brentjens.

Thats because ACTs building blocks are T cells, a type of immune cell collected from the patients own blood. After collection, the T cells are genetically engineered to produce special receptors on their surface called chimeric antigen receptors (CARs). CARs are proteins that allow the T cells to recognize a specific protein (antigen) on tumor cells. These engineered CAR T cells are then grown in the laboratory until they number in the billions.

The expanded population of CAR T cells is then infused into the patient. After the infusion, if all goes as planned, the T cells multiply in the patients body and, with guidance from their engineered receptor, recognize and kill cancer cells that harbor the antigen on their surfaces.

Although adoptive cell transfer has been restricted to small clinical trials so far, treatments using these engineered immune cells have generated some remarkable responses in patients with advanced cancer.

This process builds on a similar form of ACT pioneered by Steven Rosenberg, M.D., Ph.D., and his colleagues from NCIs Surgery Branch for patients with advanced melanoma.

The CAR T cells are much more potent than anything we can achieve with other immune-based treatments being studied, said Crystal Mackall, M.D., of NCIs Pediatric Oncology Branch (POB).

Even so, investigators working in this field caution that there is still much to learn about CAR T-cell therapy. But the early results from trials like these have generated considerable optimism.

CAR T-cell therapy eventually may become a standard therapy for some B-cell malignancies like ALL and chronic lymphocytic leukemia, Dr. Rosenberg wrote in a Nature Reviews Clinical Oncology article.

More than 80 percent of children who are diagnosed with ALL that arises in B cellsthe predominant type of pediatric ALLwill be cured by intensive chemotherapy.

For patients whose cancers return after intensive chemotherapy or a stem cell transplant, the remaining treatment options are close to none, said Stephan Grupp, M.D., Ph.D., of the Childrens Hospital of Philadelphia (CHOP) and the lead investigator of a trial testing CAR T cells primarily in children with ALL. This treatment may represent a much-needed new option for such patients, he said.

Trials of CAR T cells in adults and children with leukemia and lymphoma have used T cells engineered to target the CD19 antigen, which is present on the surface of nearly all B cells, both normal and cancerous.

In the CHOP trial, which is being conducted in collaboration with researchers from the University of Pennsylvania, all signs of cancer disappeared (a complete response) in 27 of the 30 patients treated in the study, according to findings published October 16 in the New England Journal of Medicine.

Nineteen of the 27 patients with complete responses have remained in remission, the study authors reported, with 15 of these patients receiving no further therapy and 4 patients withdrawing from the trial to receive other therapy.

According to the most recent data from a POB trial that included children with ALL, 14 of 20 patients had a complete response. And of the 12 patients who had no evidence of leukemic cells, called blasts, in their bone marrow after CAR T-cell treatment, 10 have gone on to receive a stem cell transplant and remain cancer free, reported the studys lead investigator, Daniel W. Lee, M.D., also of the POB.

Dr. Crystal Mackall

Our findings strongly suggest that CAR T-cell therapy is a useful bridge to bone marrow transplant for patients who are no longer responding to chemotherapy, Dr. Lee said.

Similar results have been seen in phase I trials of adult patients conducted at MSKCC and NCI.

In findings published in February 2014, 14 of the 16 participants in the MSKCC trial treated to that point had experienced complete responses, which in some cases occurred 2 weeks or sooner after treatment began. Of those patients who were eligible, 7 underwent a stem cell transplant and are still cancer free.

The NCI-led trial of CAR T cells included 15 adult patients, the majority of whom had advanced diffuse large B-cell lymphoma. Most patients in the trial had either complete or partial responses, reported James Kochenderfer, M.D., and his NCI colleagues.

Our data provide the first true glimpse of the potential of this approach in patients with aggressive lymphomas that, until this point, were virtually untreatable, Dr. Kochenderfer said. [NCI Surgery Branch researchers have also reported promising results from one of the first trials testing CAR T cells derived from donors, rather than the patients themselves, to treat leukemia and lymphoma.]

Other findings from the trials have been encouraging, as well. For example, the number of CAR T cells increased dramatically after infusion into patients, as much as 1,000-fold in some individuals. In addition, after infusion, CAR T cells were detected in the central nervous system, a so-called sanctuary site where solitary cancer cells that have evaded chemotherapy or radiation may hide. In two patients in the NCI pediatric trial, the CAR T-cell treatment eradicated cancer that had spread to the central nervous system.

If CAR T cells can persist at these sites, it could help fend off relapses, Dr. Mackall noted.

CAR T-cell therapy can cause several worrisome side effects, perhaps the most troublesome being cytokine-release syndrome.

The infused T cells release cytokines, which are chemical messengers that help the T cells carry out their duties. With cytokine-release syndrome, there is a rapid and massive release of cytokines into the bloodstream, which can lead to dangerously high fevers and precipitous drops in blood pressure.

Cytokine-release syndrome is a common problem in patients treated with CAR T cells. In the POB and CHOP trials, patients with the most extensive disease prior to receiving the CAR T cells were more likely to experience severe cases of cytokine-release syndrome.

For most patients, trial investigators have reported, the side effects are mild enough that they can be managed with standard supportive therapies, including steroids.

The research team at CHOP noticed that patients experiencing severe reactions all had particularly high levels of IL-6, a cytokine that is secreted by T cells and macrophages in response to inflammation. So they turned to two drugs that are approved to treat inflammatory conditions like juvenile arthritis: etanercept (Enbrel) and tocilizumab (Actemra), the latter of which blocks IL-6 activity.

The patients had excellent responses to the treatment, Dr. Grupp said. We believe that [these drugs] will be a major part of toxicity management for these patients.

The other two teams subsequently used tocilizumab in several patients. Dr. Brentjens agreed that both drugs could become a useful way to help manage cytokine-release syndrome because, unlike steroids, they dont appear to affect the infused CAR T cells activity or proliferation.

Even with these encouraging preliminary findings, more research is needed before CAR T-cell therapy becomes a routine option for patients with ALL.

We need to treat more patients and have longer follow-up to really say what the impact of this therapy is [and] to understand its true performance characteristics, Dr. Grupp said.

We need to treat more patients and have longer follow-up to really say what the impact of this therapy is [and] to understand its true performance characteristics.

Dr. Stephan Grupp

Several other trials testing CAR T cells in children and adults are ongoing and, with greater interest and involvement from the pharmaceutical and biotechnology sector, more trials testing CAR T cells are being planned.

Researchers are also studying ways to improve on the positive results obtained to date, including refining the process by which the CAR T cells are produced.

Research groups like Dr. Brentjens are also working to make a superior CAR T cell, including developing a better receptor and identifying better targets.

For example, Dr. Lee and his colleagues at NCI have developed CAR T cells that target the CD22 antigen, which is also present on most B cells, although in smaller quantities than CD19. The CD22-targeted T cells, he believes, could be used in concert with CD19-targeted T cells as a one-two punch in ALL and other B-cell cancers. NCI researchers hope to begin the first clinical trial testing the CD22-targeted CAR T cells in November 2014.

Based on the success thus far, several research groups across the country are turning their attention to developing engineered T cells for other cancers, including solid tumorslike pancreatic and brain cancers.

The stage has now been set for greater progress, Dr. Lee believes.

NCI investigators, for example, now have a platform to plug and play better CARs into that system, without a lot of additional R&D time, he continued. Everything else should now come more rapidly.

Link:
CAR T-Cell Immunotherapy for ALL - National Cancer Institute

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European Society of Gene and Cell Therapy Congress, 17-20 September 2015, Helsinki,Finland (ESGCT 2015)

4th International Conference and Exhibition on Cell & Gene Therapy, August 10-12, 2015, London (CGT 2015)

The International Society for Stem Cell Research Annual Meeting, 24th-27th June 2015, Stockholm, Sweden (ISSCR 2015)

British Society for Gene and Cell Therapy Annual Conference, 9th-11th June 2015, Strathclyde, Glasgow (BSGCT 2015)

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