Grupp Laboratory Research Overview

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. Children and adults with the Philadelphia chromosome-like subtype (Ph-like ALL) have high risk of relapse and poor outcomes when treated with conventional chemotherapy.

Researchers in the Center for Childhood Cancer Research, including Sarah K. Tasian, MD, are characterizing perturbations in signal transduction networks in high-risk pediatric leukemias, including ALL and acute myeloid leukemia (AML). Their aim is to identify hyperactive leukemia-associated signaling networks that can be treated with targeted kinase inhibitors that may help to improve clinical outcomes.

Dr. Tasian and other investigators have demonstrated hyperactivity of specific cancer signaling networks in subtypes of childhood Ph-like ALL, including activated JAK/STAT and PI3K/mTOR signaling. Prior studies by the Tasian Laboratory and other CCCR investigators reported preclinical efficacy of specific kinase inhibitors in models of childhood Ph-like ALL.

Ongoing studies in the Tasian Laboratory are currently evaluating the efficacy of PI3K pathway inhibitors in Ph-like and other genetic subtypes of ALL. Results to date demonstrate effectiveness of targeting PI3K pathway signaling, as well as suggest that rationally designed combination regimens of kinase inhibitors may also be effective therapies for children with Ph-like ALL.

Results from these laboratory studies to date have directly led to clinical trials testing kinase inhibitors in children with high-risk types of ALL.

GD2 is a complex sugar — a ganglioside — found on the surface of neuroblastoma cells, making it a good choice for targeted CAR T-cell therapy. GD2 is already being targeted by a recently FDA-approved immunotherapeutic drug called dinutuximab, an antibody that sticks to GD2 and activates the immune response to destroy the cell.

In previous clinical trials, dinutuximab increased survival in children with high-risk neuroblastoma by 20% and is presently standard of care for high-risk neuroblastoma. Despite its effectiveness, however, it is associated with a significant amount of pain during its infusion, as GD2 receptors are also located on peripheral nerves. This causes such significant neuropathy that pain management medications are administered concomitantly for the four- or five-day duration of treatment.

David Barrett, MD, PhD, and researchers at the Center for Childhood Cancer Research are developing CAR T-cell therapy for neuroblastoma with the aim of increasing the survival rate past the 55% upper limit seen with dinutuximab. They also aim to target GD2 on the neuroblastoma cells, but not the peripheral nerves. This is a challenge, particularly taking into account the fact that CAR T-cell therapy involves permanent modification of T-cells.

Once T-cells are modified and reinfused, they divide perpetually and cannot be removed from the body. Dinutuximab is an antibody that is limited in its distribution and is cleared by the body after infusion stops. CAR-modified T-cells are not; they can go many places simple antibodies cannot, and they cannot be cleared post-infusion.

Researchers are using RNA — rather than DNA — to modify the T-cells in an attempt to limit the life of the modified T-cells for this CART therapy. Over time, RNA cannot sustain replication the way DNA can, and will degrade, rendering the CAR-modified T-cell incapable of indefinite replication.

Using RNA transfection, researchers are creating a short-term CART therapy to assess its safety and efficacy. If the therapy is determined to not be associated with GD2-mediated peripheral neuropathy, subsequent efforts will make permanent alterations to the genome of the T-cells for continuous endogenous management of neuroblastoma.

These efforts are part of a Stand Up to Cancer, St. Baldrick's Foundation Pediatric Immunogenomics Dream Team grant, a four-year grant awarded to Children’s Hospital of Philadelphia and six other centers. This effort is being conducted across all cancer types to lead to identification of specific cellular surface antigens that can be targeted by CART therapy, and potentially decreasing the need for more toxic anticancer therapies in the future.

Shannon Maude, MD, PhD, and Stephan Grupp, MD, PhD, in partnership with the University of Pennsylvania and Novartis, are developing and evaluating chimeric antigen receptor (CAR) T cells to treat children with acute lymphoblastic leukemia (ALL).

T-cells can be engineered to target specific antigens on the surface of leukemic cells. After infusion into patients, CAR T-cells bind to tumor target antigens, which in turn induces an immune effector cell cytotoxic response that kills malignant cancer cells.

Remission rates exceeding 90% were seen in a Phase I/IIa trial of CAR T cells targeting CD19, but some patients relapse. A Phase 1 trial led by Dr. Maude is underway to evaluate the safety and efficacy of humanized CAR T cells targeting CD19 (CART19) as a treatment for pediatric patients with chemotherapy resistant or refractory CD19+ ALL and lymphoma.

Another clinical study is assessing the safety and efficacy of CAR T-cells targeting CD22 (CART22), another antigen expressed on ALL cancer cells, in children who relapse after CART19 treatment with CD19-negative leukemias.

Both studies will better define the utility of CAR T-cell immunotherapy as a treatment for high-risk pediatric leukemias and pediatric lymphomas.

Clinical trials are underway to evaluate the use of sirolimus as a treatment for refractory pediatric autoimmune diseases.

Autoimmune lymphoproliferative syndrome (ALPS), a disorder of abnormal lymphocyte survival, is caused by dysregulation of the FAS apoptotic (programmed cell death) pathway. Patients with ALPS develop chronic, non-malignant lymphoproliferation, autoimmune disease, and approximately 10% develop secondary malignancies. ALPS was originally thought to be extremely rare, but more patients are being diagnosed because of growing clinical awareness.

Preclinical studies using mouse xenograft models of ALPS conducted by David Teachey, MD, and researchers at the Center for Childhood Cancer Research demonstrated that PI3K/AKT/mTOR protein kinase signaling is dysregulated in ALPS. They also found that targeting ALPS with the mTOR inhibitor sirolimus (rapamycin) is effective.

Pilot clinical studies with as many as 50 pediatric patients with ALPS revealed that sirolimus treatments resulted in a complete and durable response in more than 90% of sirolimus-treated patients with minimal toxicity. Prior to using sirolimus for ALPS, there was no effective treatment that could improve the lymphoproliferative and autoimmune manifestations of the disease.

Based on the results of the pilot study, clinical trials are underway to evaluate the use of sirolimus as a treatment for refractory pediatric autoimmune diseases. Sirolimus is becoming the standard of care as a single agent targeted therapy to treat children with ALPS.

Researchers at the Center for Childhood Cancer Research successfully used engineered T cell immunotherapies to treat pediatric patients with several B-cell malignancies including acute lymphoblastic leukemia (ALL) and non-Hodgkin lymphoma (NHL). Sometimes, however, in vitro expansion of T cell populations required for these treatments has been problematic, limiting the use of T cell immunotherapies as a treatment option for children with B-cell malignancies.

Clinical studies with newly diagnosed children with ALL and NHL showed that patients with T cell populations containing large numbers of early lineage T cell subtypes (naïve and stem central memory cells) expanded better in vitro than patient T cell populations not enriched with those cell subtypes.

Also, early lineage cells were selectively depleted in T cell populations from pediatric patients treated with conventional chemotherapy. The addition of interleukin (IL) -7 and IL-15 to patient T cell cultures enriched certain early lineage cells and rescued T cell expansion capability. Other studies demonstrated that patients with ALL had higher numbers of early lineage cells and greater expansion capability than T cells from patients with NHL.

The results from these studies demonstrated that early lineage cells are essential for T cell fitness for expansion and enrichment of these populations—either by timing of T cell collection (prior to chemotherapy) or culture method—can increase the number of patients with B cell malignancies who may be eligible for treatment with engineered T cell immunotherapies.

Pediatric acute myeloid leukemia (AML) is a genetically heterogeneous disease. This has made it difficult to establish relationships between specific genetic alterations and treatment response or disease progression/relapse. Developing new therapies to treat pediatric and adolescent AML has also been hindered by this heterogeneity.

Under the direction of Richard Aplenc, MD, PhD, MSCE, researchers at the Center for Childhood Cancer Research are analyzing clinical samples and medical outcomes data from Children Oncology Group-sponsored AML clinical trials to establish possible molecular links between specific AML germline variants and treatment response.

While preliminary results from these analyses look somewhat promising, additional genome and whole exome sequencing studies are necessary to confirm links between specific genetic alterations and clinical outcomes or treatment responses for pediatric AML. Also, these analyses may help to identify new molecular targets for novel targeted cancer therapies to treat children and young adults with AML.

Researchers performed chart review for 12 different adverse events (AEs) for pediatric patients enrolled in U.S.-based Cancer Oncology Group (COG) Phase III clinical trials for pediatric acute myeloid leukemia (AML). Results from this analysis showed the current system of AE reporting on cooperative group oncology trials had modest sensitivity and a demonstrable false positive rate.

Cooperative group oncology clinical trials have led to improvements in the survival outcomes of children with cancer. However, the large number of side effects from treatment, coupled with a growing list of ways to report treatment toxicities, has called into question the accuracy of AE reporting in pediatric clinical trials.

In most cooperative oncology group pediatric trials, AEs are reported manually by clinical research associates via case report forms using the National Cancer Institute Common Terminology Criteria for Adverse Events system. Yet, despite extensive time required for AE reporting, there is growing evidence that AEs may be underreported or reported incorrectly in pediatric cancer clinical trials.

Tamara P. Miller, MD, MSCE, and researchers at the Center for Childhood Cancer Research performed chart review for 12 different AEs for pediatric patients enrolled on a COG Phase III clinical trial for pediatric AML. Chart abstraction was performed on more than 200 patients who underwent multiple rounds of chemotherapy for AML. The reports of AEs on the clinical trial were then compared to the results of the chart review. Results from this analysis showed the current system of AE reporting on cooperative group oncology trials had less than 50% sensitivity for eight of 12 AEs and a demonstrable false positive rate.

Studies are currently underway to develop new methods to improve the sensitivity and accuracy of AE reporting in clinical trials for children with cancer.

Modifying patient T-cells with chimeric antigen receptors (CARs) and then reinfusing them has been shown in clinical trials to be an effective treatment for certain forms of cancer. However, the use of a CART-19 therapy has been associated with a significant increase in the production of cytokines that can make patients ill.

A cytokine is a chemical that helps mobilize the cells of the immune system when a response is required. In the case of CART-19 in patients with leukemia, the cytokine overexpressed is interleukin (IL)-6. While the CART-19 is effectively killing leukemic cells, the modified T-cells, likely in conjunction with other cells in the immune system, are also producing IL-6 at high levels in some patients, making those patients extremely ill.

This is particularly worrisome since CAR T-cell therapy involves the permanent modification of T-cells — once reinfused into the body they cannot be removed, and the toxic effects of the therapy would be perpetuated indefinitely. Fortunately, there is an antidote for IL-6, called tocilizumab.

Researchers at the Center for Childhood Cancer Research, including David Barrett, MD, PhD, are studying T-cells from patients enrolled in a CART-19 clinical trial for leukemia. They aim to identify the genes that trigger the excessive release of IL-6 using the cells in vitro and working with animal models.

Once those biomarkers have been discovered, at-risk children can be identified and earlier intervention provided should cytokine release syndrome occur.

If patients at a higher risk for developing cytokine release syndrome can undergo co-therapy of CART-19 and tocilizumab from the outset of treatment, perhaps the release of IL-6 can be stemmed at the start, allowing the CART-19 to work without the concomitant toxic effects associated with cytokine release syndrome. Researchers are also hope to determine whether co-therapy with tocilizumab as a matter of course in all patients treated with CART-19 will impair the effectiveness of CART-19.

If IL-6 is not necessary for the clinical response to CART-19, then all patients undergoing CART-19 therapy can be co-administered tocilizumab at the start of therapy. However, if tocilizumab impairs clinical response, its use needs to be limited to the population of patients most likely to be sickened by CART-19 therapy.

A Phase II registration trial for submission to the FDA is presently underway to understand, predict, and prevent cytokine release syndrome; an international clinical trial of CART-19 will begin soon.