ALL

Lab mice

Credit: Aaron Logan

Two papers published in Nature Immunology have shed new light on the role of Ikaros in B-cell acute lymphoblastic leukemia (B-ALL).

In one paper, researchers describe experiments in mice that show a defect in Ikaros function can disrupt lymphopoiesis and prevent the development of mature B cells.

The cells stay in an aberrant state, which closely resembles that of cells in human B-ALL.

The other paper provides insight into how pre-B cells transition from a proliferative phase to a differentiation phase.

Investigators found that this process, which is vulnerable to leukemic transformation, is dependent upon Ikaros.

Ikaros defect in mice mimics human B-ALL

In the first sudy, researchers showed that loss of Ikaros function in mice creates an environment that mimics human B-ALL.

“We already know several transcription factors that play a central role in B-cell differentiation,” said study author Meinrad Busslinger, PhD, of the Research Institute of Molecular Pathology in Vienna, Austria.

“Pax5, for example, represents a critical factor which activates the B-cell-specific program in precursor cells and simultaneously suppresses alternative cell fates. For Ikaros, we did not know, until now, what this factor is doing during early B-cell development.”

To find out, he and his colleagues analyzed mice that lacked Ikaros from an early stage of B-cell development on. They found that Ikaros deficiency arrested B-cell development due to a defect in pre-BCR signaling.

The cells remained in an aberrant, pro-B-cell stage and were prevented from further differentiation. They also showed increased cell adhesion and reduced migration compared to normal cells.

The researchers noted that loss of Ikaros function has previously been associated with the development of B-ALL. As in mice with a mutated Ikaros gene, B cells from B-ALL patients are arrested at an early checkpoint of B-cell development.

Loss of Ikaros in pre-B cells

With the second study, investigators provided new insight into pre-B-cell differentiation. They described the cells’ transition from a stroma-adherent proliferative phase to a nonadherent differentiation phase.

The stroma-adherent pre-B cells were highly proliferative and had limited self-renewing potential. But when they transitioned to the nonadherent phase, they exited the cell cycle, lost their capacity for self-renewal, and acquired the expression of genes encoding molecules that support B-cell maturation.

And this transition was dependent upon Ikaros.

“Loss of function in the transcription factor Ikaros appears to create a differentiation block that drives the pre-B cells into an adhesive state, promotes self-renewal, and primes them for malignant potential,” said study author Richard Van Etten, MD, PhD, of the University of California, Irvine.

Furthermore, the survival and proliferation of the Ikaros-deficient pre-B cells appeared to be dependent on cooperation between signaling via integrins and signaling via receptors for growth factors.

The researchers said this discovery points to a new avenue for treating B-ALLs resulting from Ikaros mutations.

Lab mice

Credit: Aaron Logan

Two papers published in Nature Immunology have shed new light on the role of Ikaros in B-cell acute lymphoblastic leukemia (B-ALL).

In one paper, researchers describe experiments in mice that show a defect in Ikaros function can disrupt lymphopoiesis and prevent the development of mature B cells.

The cells stay in an aberrant state, which closely resembles that of cells in human B-ALL.

The other paper provides insight into how pre-B cells transition from a proliferative phase to a differentiation phase.

Investigators found that this process, which is vulnerable to leukemic transformation, is dependent upon Ikaros.

Ikaros defect in mice mimics human B-ALL

In the first sudy, researchers showed that loss of Ikaros function in mice creates an environment that mimics human B-ALL.

“We already know several transcription factors that play a central role in B-cell differentiation,” said study author Meinrad Busslinger, PhD, of the Research Institute of Molecular Pathology in Vienna, Austria.

“Pax5, for example, represents a critical factor which activates the B-cell-specific program in precursor cells and simultaneously suppresses alternative cell fates. For Ikaros, we did not know, until now, what this factor is doing during early B-cell development.”

To find out, he and his colleagues analyzed mice that lacked Ikaros from an early stage of B-cell development on. They found that Ikaros deficiency arrested B-cell development due to a defect in pre-BCR signaling.

The cells remained in an aberrant, pro-B-cell stage and were prevented from further differentiation. They also showed increased cell adhesion and reduced migration compared to normal cells.

The researchers noted that loss of Ikaros function has previously been associated with the development of B-ALL. As in mice with a mutated Ikaros gene, B cells from B-ALL patients are arrested at an early checkpoint of B-cell development.

Loss of Ikaros in pre-B cells

With the second study, investigators provided new insight into pre-B-cell differentiation. They described the cells’ transition from a stroma-adherent proliferative phase to a nonadherent differentiation phase.

The stroma-adherent pre-B cells were highly proliferative and had limited self-renewing potential. But when they transitioned to the nonadherent phase, they exited the cell cycle, lost their capacity for self-renewal, and acquired the expression of genes encoding molecules that support B-cell maturation.

And this transition was dependent upon Ikaros.

“Loss of function in the transcription factor Ikaros appears to create a differentiation block that drives the pre-B cells into an adhesive state, promotes self-renewal, and primes them for malignant potential,” said study author Richard Van Etten, MD, PhD, of the University of California, Irvine.

Furthermore, the survival and proliferation of the Ikaros-deficient pre-B cells appeared to be dependent on cooperation between signaling via integrins and signaling via receptors for growth factors.

The researchers said this discovery points to a new avenue for treating B-ALLs resulting from Ikaros mutations.

Lab mice

Credit: Aaron Logan

Two papers published in Nature Immunology have shed new light on the role of Ikaros in B-cell acute lymphoblastic leukemia (B-ALL).

In one paper, researchers describe experiments in mice that show a defect in Ikaros function can disrupt lymphopoiesis and prevent the development of mature B cells.

The cells stay in an aberrant state, which closely resembles that of cells in human B-ALL.

The other paper provides insight into how pre-B cells transition from a proliferative phase to a differentiation phase.

Investigators found that this process, which is vulnerable to leukemic transformation, is dependent upon Ikaros.

Ikaros defect in mice mimics human B-ALL

In the first sudy, researchers showed that loss of Ikaros function in mice creates an environment that mimics human B-ALL.

“We already know several transcription factors that play a central role in B-cell differentiation,” said study author Meinrad Busslinger, PhD, of the Research Institute of Molecular Pathology in Vienna, Austria.

“Pax5, for example, represents a critical factor which activates the B-cell-specific program in precursor cells and simultaneously suppresses alternative cell fates. For Ikaros, we did not know, until now, what this factor is doing during early B-cell development.”

To find out, he and his colleagues analyzed mice that lacked Ikaros from an early stage of B-cell development on. They found that Ikaros deficiency arrested B-cell development due to a defect in pre-BCR signaling.

The cells remained in an aberrant, pro-B-cell stage and were prevented from further differentiation. They also showed increased cell adhesion and reduced migration compared to normal cells.

The researchers noted that loss of Ikaros function has previously been associated with the development of B-ALL. As in mice with a mutated Ikaros gene, B cells from B-ALL patients are arrested at an early checkpoint of B-cell development.

Loss of Ikaros in pre-B cells

With the second study, investigators provided new insight into pre-B-cell differentiation. They described the cells’ transition from a stroma-adherent proliferative phase to a nonadherent differentiation phase.

The stroma-adherent pre-B cells were highly proliferative and had limited self-renewing potential. But when they transitioned to the nonadherent phase, they exited the cell cycle, lost their capacity for self-renewal, and acquired the expression of genes encoding molecules that support B-cell maturation.

And this transition was dependent upon Ikaros.

“Loss of function in the transcription factor Ikaros appears to create a differentiation block that drives the pre-B cells into an adhesive state, promotes self-renewal, and primes them for malignant potential,” said study author Richard Van Etten, MD, PhD, of the University of California, Irvine.

Furthermore, the survival and proliferation of the Ikaros-deficient pre-B cells appeared to be dependent on cooperation between signaling via integrins and signaling via receptors for growth factors.

The researchers said this discovery points to a new avenue for treating B-ALLs resulting from Ikaros mutations.

Monoclonal antibodies

Credit: Linda Bartlett

Adding the alkylating agent cyclophosphamide to treatment with a monoclonal antibody (mAb) can overcome drug resistance in mice with acute lymphoblastic leukemia (ALL), researchers have reported in Cell.

mAbs such as rituximab and alemtuzumab are designed to bind to proteins found on the surfaces of tumor cells.

Once the mAbs flag the tumor cells, macrophages destroy them. But the drugs have little effect on tumor cells that hide out in the bone marrow.

Experiments in mice with B-cell ALL revealed that cyclophosphamide stimulates the immune response in bone marrow, eliminating the reservoir of cancer cells that can produce new tumors after treatment with a mAb.

Finding hidden ALL cells

Michael Hemann, PhD, of MIT’s Koch Institute for Integrative Cancer Research in Cambridge, Massachusetts, and his colleagues began this research by administering alemtuzumab to the mice.

The drug successfully cleared most ALL cells, but some remained hidden in the bone marrow, which has been identified as a site of drug resistance in many cancers.

The researchers found that, within the bone marrow, alemtuzumab successfully binds to ALL cells. But macrophages do not attack the cells due to the presence of lipid compounds called prostaglandins, which repress macrophage activity.

Scientists believe the bone marrow naturally produces prostaglandins to help protect the immune cells maturing there. Tumor cells that reach the bone marrow can exploit this protective environment to aid their own survival.

The finding is an important contribution to scientists’ understanding of how mAbs act against ALL, according to Ravi Majeti, MD, PhD, of Stanford University in California, who was not involved in this research.

“There clearly has been a lack of understanding about why antibody therapies have been relatively unsuccessful as monotherapies,” Dr Majeti said.

Tricking the immune system

Dr Hemann and his colleagues then tested a variety of anticancer drugs in combination with alemtuzumab. And they discovered that cyclophosphamide can “rewire” the bone marrow microenvironment to make it much more receptive to macrophages, allowing them to destroy the tumor cells hiding there.

“After you treat with cyclophosphamide, you get this flux of macrophages into the bone marrow, and these macrophages are now active and very capable of consuming the targeted tumor cells,” Dr Hemann said.

“Essentially, we are tricking the immune system to suddenly recognize an entity that it wouldn’t typically recognize and aggressively go after antibody-bound tumor cells.”

Following treatment with this combination, the mice survived and remained free of ALL for the duration of the study, which was about 18 months.

However, the researchers found that timing of drug delivery was critical. Alemtuzumab and cyclophosphamide must be administered together so that cyclophosphamide can create the right type of environment for macrophages to become activated in the bone marrow.

The team also obtained good results by combining cyclophosphamide with rituximab.

They now plan to test cyclophosphamide with other mAbs and begin testing the alemtuzumab-cyclophosphamide combination in patients.

Monoclonal antibodies

Credit: Linda Bartlett

Adding the alkylating agent cyclophosphamide to treatment with a monoclonal antibody (mAb) can overcome drug resistance in mice with acute lymphoblastic leukemia (ALL), researchers have reported in Cell.

mAbs such as rituximab and alemtuzumab are designed to bind to proteins found on the surfaces of tumor cells.

Once the mAbs flag the tumor cells, macrophages destroy them. But the drugs have little effect on tumor cells that hide out in the bone marrow.

Experiments in mice with B-cell ALL revealed that cyclophosphamide stimulates the immune response in bone marrow, eliminating the reservoir of cancer cells that can produce new tumors after treatment with a mAb.

Finding hidden ALL cells

Michael Hemann, PhD, of MIT’s Koch Institute for Integrative Cancer Research in Cambridge, Massachusetts, and his colleagues began this research by administering alemtuzumab to the mice.

The drug successfully cleared most ALL cells, but some remained hidden in the bone marrow, which has been identified as a site of drug resistance in many cancers.

The researchers found that, within the bone marrow, alemtuzumab successfully binds to ALL cells. But macrophages do not attack the cells due to the presence of lipid compounds called prostaglandins, which repress macrophage activity.

Scientists believe the bone marrow naturally produces prostaglandins to help protect the immune cells maturing there. Tumor cells that reach the bone marrow can exploit this protective environment to aid their own survival.

The finding is an important contribution to scientists’ understanding of how mAbs act against ALL, according to Ravi Majeti, MD, PhD, of Stanford University in California, who was not involved in this research.

“There clearly has been a lack of understanding about why antibody therapies have been relatively unsuccessful as monotherapies,” Dr Majeti said.

Tricking the immune system

Dr Hemann and his colleagues then tested a variety of anticancer drugs in combination with alemtuzumab. And they discovered that cyclophosphamide can “rewire” the bone marrow microenvironment to make it much more receptive to macrophages, allowing them to destroy the tumor cells hiding there.

“After you treat with cyclophosphamide, you get this flux of macrophages into the bone marrow, and these macrophages are now active and very capable of consuming the targeted tumor cells,” Dr Hemann said.

“Essentially, we are tricking the immune system to suddenly recognize an entity that it wouldn’t typically recognize and aggressively go after antibody-bound tumor cells.”

Following treatment with this combination, the mice survived and remained free of ALL for the duration of the study, which was about 18 months.

However, the researchers found that timing of drug delivery was critical. Alemtuzumab and cyclophosphamide must be administered together so that cyclophosphamide can create the right type of environment for macrophages to become activated in the bone marrow.

The team also obtained good results by combining cyclophosphamide with rituximab.

They now plan to test cyclophosphamide with other mAbs and begin testing the alemtuzumab-cyclophosphamide combination in patients.

Monoclonal antibodies

Credit: Linda Bartlett

Adding the alkylating agent cyclophosphamide to treatment with a monoclonal antibody (mAb) can overcome drug resistance in mice with acute lymphoblastic leukemia (ALL), researchers have reported in Cell.

mAbs such as rituximab and alemtuzumab are designed to bind to proteins found on the surfaces of tumor cells.

Once the mAbs flag the tumor cells, macrophages destroy them. But the drugs have little effect on tumor cells that hide out in the bone marrow.

Experiments in mice with B-cell ALL revealed that cyclophosphamide stimulates the immune response in bone marrow, eliminating the reservoir of cancer cells that can produce new tumors after treatment with a mAb.

Finding hidden ALL cells

Michael Hemann, PhD, of MIT’s Koch Institute for Integrative Cancer Research in Cambridge, Massachusetts, and his colleagues began this research by administering alemtuzumab to the mice.

The drug successfully cleared most ALL cells, but some remained hidden in the bone marrow, which has been identified as a site of drug resistance in many cancers.

The researchers found that, within the bone marrow, alemtuzumab successfully binds to ALL cells. But macrophages do not attack the cells due to the presence of lipid compounds called prostaglandins, which repress macrophage activity.

Scientists believe the bone marrow naturally produces prostaglandins to help protect the immune cells maturing there. Tumor cells that reach the bone marrow can exploit this protective environment to aid their own survival.

The finding is an important contribution to scientists’ understanding of how mAbs act against ALL, according to Ravi Majeti, MD, PhD, of Stanford University in California, who was not involved in this research.

“There clearly has been a lack of understanding about why antibody therapies have been relatively unsuccessful as monotherapies,” Dr Majeti said.

Tricking the immune system

Dr Hemann and his colleagues then tested a variety of anticancer drugs in combination with alemtuzumab. And they discovered that cyclophosphamide can “rewire” the bone marrow microenvironment to make it much more receptive to macrophages, allowing them to destroy the tumor cells hiding there.

“After you treat with cyclophosphamide, you get this flux of macrophages into the bone marrow, and these macrophages are now active and very capable of consuming the targeted tumor cells,” Dr Hemann said.

“Essentially, we are tricking the immune system to suddenly recognize an entity that it wouldn’t typically recognize and aggressively go after antibody-bound tumor cells.”

Following treatment with this combination, the mice survived and remained free of ALL for the duration of the study, which was about 18 months.

However, the researchers found that timing of drug delivery was critical. Alemtuzumab and cyclophosphamide must be administered together so that cyclophosphamide can create the right type of environment for macrophages to become activated in the bone marrow.

The team also obtained good results by combining cyclophosphamide with rituximab.

They now plan to test cyclophosphamide with other mAbs and begin testing the alemtuzumab-cyclophosphamide combination in patients.

Less than 3 months after it was pulled from the market due to safety concerns, ponatinib (Iclusig) is once again commercially available in the US.

Ariad Pharmaceuticals, Inc., has begun shipping the drug to Biologics, Inc., its exclusive specialty pharmacy. And the pharmacy has started filling prescriptions and distributing ponatinib to patients in need.

The drug is approved by the US Food and Drug Administration (FDA) to treat chronic myeloid leukemia (CML) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) that is resistant to or intolerant of other tyrosine kinase inhibitors (TKIs).

Safety concerns prompt action

Last October, the latest results of the phase 2 PACE trial revealed that ponatinib can increase a patient’s risk of arterial and venous thrombotic events. So all trials of the drug were placed on partial clinical hold, with the exception of the phase 3 EPIC trial, which was discontinued.

Then, the FDA suspended sales and marketing of ponatinib, pending results of a safety evaluation. But in December, the agency decided the drug could return to the market if new safety measures were implemented.

The FDA approved revised prescribing information and a communications Risk Evaluation and Mitigation Strategy for ponatinib. The prescribing information includes a revised indication statement and boxed warning, updated safety information, and recommendations regarding dosing considerations for prescribers.

Now, ponatinib is indicated for the treatment of:

• Adults with T315I-positive CML (chronic, accelerated, or blast phase)
• Adults with T315I-positive Ph+ ALL
• Adults with CML (chronic, accelerated, or blast phase) who cannot receive another TKI
• Adults with Ph+ ALL who cannot receive another TKI.

The starting dose of ponatinib remains 45 mg daily.

IND program

On November 1, 2013, there were approximately 640 patients receiving ponatinib through commercial channels in the US. Since then, the drug was only made available through emergency and single-patient investigational new drug (IND) applications, which were reviewed and approved by the FDA on a case-by-case basis.

The FDA has approved more than 370 INDs since early November, and more than 300 patients have received ponatinib at no cost through this process.

Ariad expects most of these patients, many of whom received a 3-month supply of ponatinib, to transition from the IND program to commercial therapy by the end of the first quarter of 2014. The IND program is now closed to new patients with Ph+ leukemias.

Ponatinib is currently priced in the US at approximately $125,000 per year. For more information on the drug, visit www.iclusig.com.

Less than 3 months after it was pulled from the market due to safety concerns, ponatinib (Iclusig) is once again commercially available in the US.

Ariad Pharmaceuticals, Inc., has begun shipping the drug to Biologics, Inc., its exclusive specialty pharmacy. And the pharmacy has started filling prescriptions and distributing ponatinib to patients in need.

The drug is approved by the US Food and Drug Administration (FDA) to treat chronic myeloid leukemia (CML) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) that is resistant to or intolerant of other tyrosine kinase inhibitors (TKIs).

Safety concerns prompt action

Last October, the latest results of the phase 2 PACE trial revealed that ponatinib can increase a patient’s risk of arterial and venous thrombotic events. So all trials of the drug were placed on partial clinical hold, with the exception of the phase 3 EPIC trial, which was discontinued.

Then, the FDA suspended sales and marketing of ponatinib, pending results of a safety evaluation. But in December, the agency decided the drug could return to the market if new safety measures were implemented.

The FDA approved revised prescribing information and a communications Risk Evaluation and Mitigation Strategy for ponatinib. The prescribing information includes a revised indication statement and boxed warning, updated safety information, and recommendations regarding dosing considerations for prescribers.

Now, ponatinib is indicated for the treatment of:

• Adults with T315I-positive CML (chronic, accelerated, or blast phase)
• Adults with T315I-positive Ph+ ALL
• Adults with CML (chronic, accelerated, or blast phase) who cannot receive another TKI
• Adults with Ph+ ALL who cannot receive another TKI.

The starting dose of ponatinib remains 45 mg daily.

IND program

On November 1, 2013, there were approximately 640 patients receiving ponatinib through commercial channels in the US. Since then, the drug was only made available through emergency and single-patient investigational new drug (IND) applications, which were reviewed and approved by the FDA on a case-by-case basis.

The FDA has approved more than 370 INDs since early November, and more than 300 patients have received ponatinib at no cost through this process.

Ariad expects most of these patients, many of whom received a 3-month supply of ponatinib, to transition from the IND program to commercial therapy by the end of the first quarter of 2014. The IND program is now closed to new patients with Ph+ leukemias.

Ponatinib is currently priced in the US at approximately $125,000 per year. For more information on the drug, visit www.iclusig.com.

Less than 3 months after it was pulled from the market due to safety concerns, ponatinib (Iclusig) is once again commercially available in the US.

Ariad Pharmaceuticals, Inc., has begun shipping the drug to Biologics, Inc., its exclusive specialty pharmacy. And the pharmacy has started filling prescriptions and distributing ponatinib to patients in need.

The drug is approved by the US Food and Drug Administration (FDA) to treat chronic myeloid leukemia (CML) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) that is resistant to or intolerant of other tyrosine kinase inhibitors (TKIs).

Safety concerns prompt action

Last October, the latest results of the phase 2 PACE trial revealed that ponatinib can increase a patient’s risk of arterial and venous thrombotic events. So all trials of the drug were placed on partial clinical hold, with the exception of the phase 3 EPIC trial, which was discontinued.

Then, the FDA suspended sales and marketing of ponatinib, pending results of a safety evaluation. But in December, the agency decided the drug could return to the market if new safety measures were implemented.

The FDA approved revised prescribing information and a communications Risk Evaluation and Mitigation Strategy for ponatinib. The prescribing information includes a revised indication statement and boxed warning, updated safety information, and recommendations regarding dosing considerations for prescribers.

Now, ponatinib is indicated for the treatment of:

• Adults with T315I-positive CML (chronic, accelerated, or blast phase)
• Adults with T315I-positive Ph+ ALL
• Adults with CML (chronic, accelerated, or blast phase) who cannot receive another TKI
• Adults with Ph+ ALL who cannot receive another TKI.

The starting dose of ponatinib remains 45 mg daily.

IND program

On November 1, 2013, there were approximately 640 patients receiving ponatinib through commercial channels in the US. Since then, the drug was only made available through emergency and single-patient investigational new drug (IND) applications, which were reviewed and approved by the FDA on a case-by-case basis.

The FDA has approved more than 370 INDs since early November, and more than 300 patients have received ponatinib at no cost through this process.

Ariad expects most of these patients, many of whom received a 3-month supply of ponatinib, to transition from the IND program to commercial therapy by the end of the first quarter of 2014. The IND program is now closed to new patients with Ph+ leukemias.

Ponatinib is currently priced in the US at approximately $125,000 per year. For more information on the drug, visit www.iclusig.com.

Bone marrow smear from

a patient with ALL

Investigators have identified the genetic events leading to leukemic transformation in ETV6-RUNX1 acute lymphoblastic leukemia (ALL), according to a paper published in Nature Genetics.

Previous studies have shown that, for 1 in 4 ALL patients, a key factor driving the disease is a chromosomal translocation that creates the ETV6-RUNX1 fusion gene.

However, the gene cannot cause overt leukemia on its own. Additional mutations are required for ALL to develop.

In this study, researchers found that RAG proteins—which rearrange the genome in normal immune cells to generate antibody diversity—can also rearrange the DNA of genes involved in cancer.

And this leads to ALL in individuals with the ETV6-RUNX1 fusion gene.

“For the first time, we see the combined events that are driving this treatable but highly devastating disease,” said lead study author Elli Papaemmanuil, PhD, of the Wellcome Trust Sanger Institute in Hinxton, UK.

“We now have a better understanding of the natural history of this disease and the critical events—from the initial acquisition of the fusion ETV6-RUNX1 to the sequential acquisition of RAG-mediated genome alterations—that ultimately result in this childhood leukemia.”

To unearth this discovery, the investigators sequenced the genomes of 57 ALL patients with the fusion gene. The team found that genomic rearrangements, and deletions in particular, were the predominant drivers of leukemia.

All samples showed evidence of events involving the RAG proteins. The proteins use a unique sequence of DNA letters as a signpost to direct them to antibody regions.

The researchers discovered that remnants of this sequence lay close to more than 50% of the cancer-driving genetic rearrangements. And this process often prompted the loss of the very genes required for normal immune cell development.

It is the deletion of these genes that, in combination with the fusion gene, leads to ALL, the investigators said. And the genetic signature linking the RAG proteins to genomic instability is not found in other types of leukemia or other common cancers.

“In this childhood leukemia, we see that the very process required to make normal antibodies is co-opted by the leukemia cells to knock out other genes with unprecedented specificity,” said Peter Campbell, PhD, also of the Wellcome Trust Sanger Institute.

To better understand the events that led to ALL development, the researchers used single-cell genomics to analyze samples from 2 patients. The team found that the cancer-causing process they identified occurs many times and results in continuous diversification of the leukemia.

“It may seem surprising that evolution should have provided a mechanism for diversifying antibodies that can collaterally damage genes that then contribute to cancer,” said Mel Greaves, PhD, of The Institute of Cancer Research in London, UK.

“But this only happens because the fusion gene that initiates the disease ‘traps’ cells in a normally very transient window of cell development where the RAG enzymes are active, teasing out their imperfect specificity.”

The researchers are now planning to investigate how the RAG-mediated genomic instability accrues in cells with the ETV6-RUNX1 fusion gene and what role this process plays in patients who relapse.

Bone marrow smear from

a patient with ALL

Investigators have identified the genetic events leading to leukemic transformation in ETV6-RUNX1 acute lymphoblastic leukemia (ALL), according to a paper published in Nature Genetics.

Previous studies have shown that, for 1 in 4 ALL patients, a key factor driving the disease is a chromosomal translocation that creates the ETV6-RUNX1 fusion gene.

However, the gene cannot cause overt leukemia on its own. Additional mutations are required for ALL to develop.

In this study, researchers found that RAG proteins—which rearrange the genome in normal immune cells to generate antibody diversity—can also rearrange the DNA of genes involved in cancer.

And this leads to ALL in individuals with the ETV6-RUNX1 fusion gene.

“For the first time, we see the combined events that are driving this treatable but highly devastating disease,” said lead study author Elli Papaemmanuil, PhD, of the Wellcome Trust Sanger Institute in Hinxton, UK.

“We now have a better understanding of the natural history of this disease and the critical events—from the initial acquisition of the fusion ETV6-RUNX1 to the sequential acquisition of RAG-mediated genome alterations—that ultimately result in this childhood leukemia.”

To unearth this discovery, the investigators sequenced the genomes of 57 ALL patients with the fusion gene. The team found that genomic rearrangements, and deletions in particular, were the predominant drivers of leukemia.

All samples showed evidence of events involving the RAG proteins. The proteins use a unique sequence of DNA letters as a signpost to direct them to antibody regions.

The researchers discovered that remnants of this sequence lay close to more than 50% of the cancer-driving genetic rearrangements. And this process often prompted the loss of the very genes required for normal immune cell development.

It is the deletion of these genes that, in combination with the fusion gene, leads to ALL, the investigators said. And the genetic signature linking the RAG proteins to genomic instability is not found in other types of leukemia or other common cancers.

“In this childhood leukemia, we see that the very process required to make normal antibodies is co-opted by the leukemia cells to knock out other genes with unprecedented specificity,” said Peter Campbell, PhD, also of the Wellcome Trust Sanger Institute.

To better understand the events that led to ALL development, the researchers used single-cell genomics to analyze samples from 2 patients. The team found that the cancer-causing process they identified occurs many times and results in continuous diversification of the leukemia.

“It may seem surprising that evolution should have provided a mechanism for diversifying antibodies that can collaterally damage genes that then contribute to cancer,” said Mel Greaves, PhD, of The Institute of Cancer Research in London, UK.

“But this only happens because the fusion gene that initiates the disease ‘traps’ cells in a normally very transient window of cell development where the RAG enzymes are active, teasing out their imperfect specificity.”

The researchers are now planning to investigate how the RAG-mediated genomic instability accrues in cells with the ETV6-RUNX1 fusion gene and what role this process plays in patients who relapse.

Bone marrow smear from

a patient with ALL

Investigators have identified the genetic events leading to leukemic transformation in ETV6-RUNX1 acute lymphoblastic leukemia (ALL), according to a paper published in Nature Genetics.

Previous studies have shown that, for 1 in 4 ALL patients, a key factor driving the disease is a chromosomal translocation that creates the ETV6-RUNX1 fusion gene.

However, the gene cannot cause overt leukemia on its own. Additional mutations are required for ALL to develop.

In this study, researchers found that RAG proteins—which rearrange the genome in normal immune cells to generate antibody diversity—can also rearrange the DNA of genes involved in cancer.

And this leads to ALL in individuals with the ETV6-RUNX1 fusion gene.

“For the first time, we see the combined events that are driving this treatable but highly devastating disease,” said lead study author Elli Papaemmanuil, PhD, of the Wellcome Trust Sanger Institute in Hinxton, UK.

“We now have a better understanding of the natural history of this disease and the critical events—from the initial acquisition of the fusion ETV6-RUNX1 to the sequential acquisition of RAG-mediated genome alterations—that ultimately result in this childhood leukemia.”

To unearth this discovery, the investigators sequenced the genomes of 57 ALL patients with the fusion gene. The team found that genomic rearrangements, and deletions in particular, were the predominant drivers of leukemia.

All samples showed evidence of events involving the RAG proteins. The proteins use a unique sequence of DNA letters as a signpost to direct them to antibody regions.

The researchers discovered that remnants of this sequence lay close to more than 50% of the cancer-driving genetic rearrangements. And this process often prompted the loss of the very genes required for normal immune cell development.

It is the deletion of these genes that, in combination with the fusion gene, leads to ALL, the investigators said. And the genetic signature linking the RAG proteins to genomic instability is not found in other types of leukemia or other common cancers.

“In this childhood leukemia, we see that the very process required to make normal antibodies is co-opted by the leukemia cells to knock out other genes with unprecedented specificity,” said Peter Campbell, PhD, also of the Wellcome Trust Sanger Institute.

To better understand the events that led to ALL development, the researchers used single-cell genomics to analyze samples from 2 patients. The team found that the cancer-causing process they identified occurs many times and results in continuous diversification of the leukemia.

“It may seem surprising that evolution should have provided a mechanism for diversifying antibodies that can collaterally damage genes that then contribute to cancer,” said Mel Greaves, PhD, of The Institute of Cancer Research in London, UK.

“But this only happens because the fusion gene that initiates the disease ‘traps’ cells in a normally very transient window of cell development where the RAG enzymes are active, teasing out their imperfect specificity.”

The researchers are now planning to investigate how the RAG-mediated genomic instability accrues in cells with the ETV6-RUNX1 fusion gene and what role this process plays in patients who relapse.

Genetically modified zebrafish

Experiments in zebrafish have shown that a 50-year-old antipsychotic medication called perphenazine can actively combat T-cell acute lymphoblastic leukemia (T-ALL).

The drug works by turning on a cancer-suppressing enzyme called PP2A and causing malignant tumor cells to self-destruct.

The findings suggest that developing medications that activate PP2A, while avoiding perphenazine’s psychotropic effects, could help clinicians make much-needed headway against T-ALL and perhaps other tumors as well.

Alejandro Gutierrez, MD, of the Dana-Farber Cancer Institute in Boston, and his colleagues detailed this research in The Journal of Clinical Investigation.

The researchers screened a library of 4880 compounds—including FDA-approved drugs whose patents had expired, small molecules, and natural products—in a model of T-ALL engineered using zebrafish.

One of the strongest hits in the zebrafish screen was perphenazine. The drug is a member of the phenothiazines family of antipsychotic medications, which can block dopamine receptors.

The investigators verified perphenazine’s anti-leukemic potential in vitro in several mouse and human T-ALL cell lines. Biochemical studies indicated that perphenazine’s anti-tumor activity is independent of its psychotropic activity and that it attacks T-ALL cells by turning on PP2A.

The fact that perphenazine works by reactivating a protein shut down in cancer cells is novel in the drug development field.

“We rarely find potential drug molecules that activate an enzyme,” Dr Gutierrez explained. “Most new drugs deactivate some protein or signal that the cancer cell requires to survive. But, here, perphenazine is restoring the activity of PP2A in the T-ALL cell.”

The researchers are now working to better understand the interactions between PP2A and perphenazine. They also want to search for or develop molecules that bind to and activate the enzyme more tightly and specifically to avoid perphenazine’s psychiatric effects.

“The challenge is to use medicinal chemistry to develop new PP2A inhibitors similar to perphenazine and the other phenothiazines, but to dial down dopamine interactions and accentuate those with PP2A,” said study author A. Thomas Look, MD, also of Dana-Farber.

He added that future PP2A inhibitors could be important additions to the oncologist’s arsenal. When used in combination with other drugs, the inhibitors might “make a real difference” for patients with T-ALL.

The investigators also believe the benefits of PP2A-activating drugs could extend beyond T-ALL.

“The proteins that PP2A suppresses, such as Myc and Akt, are involved in many tumors,” Dr Look noted. “We are optimistic that PP2A activators will have quite broad activity against different kinds of cancer, and we’re anxious to study the pathway in other malignancies as well.”

Genetically modified zebrafish

Experiments in zebrafish have shown that a 50-year-old antipsychotic medication called perphenazine can actively combat T-cell acute lymphoblastic leukemia (T-ALL).

The drug works by turning on a cancer-suppressing enzyme called PP2A and causing malignant tumor cells to self-destruct.

The findings suggest that developing medications that activate PP2A, while avoiding perphenazine’s psychotropic effects, could help clinicians make much-needed headway against T-ALL and perhaps other tumors as well.

Alejandro Gutierrez, MD, of the Dana-Farber Cancer Institute in Boston, and his colleagues detailed this research in The Journal of Clinical Investigation.

The researchers screened a library of 4880 compounds—including FDA-approved drugs whose patents had expired, small molecules, and natural products—in a model of T-ALL engineered using zebrafish.

One of the strongest hits in the zebrafish screen was perphenazine. The drug is a member of the phenothiazines family of antipsychotic medications, which can block dopamine receptors.

The investigators verified perphenazine’s anti-leukemic potential in vitro in several mouse and human T-ALL cell lines. Biochemical studies indicated that perphenazine’s anti-tumor activity is independent of its psychotropic activity and that it attacks T-ALL cells by turning on PP2A.

The fact that perphenazine works by reactivating a protein shut down in cancer cells is novel in the drug development field.

“We rarely find potential drug molecules that activate an enzyme,” Dr Gutierrez explained. “Most new drugs deactivate some protein or signal that the cancer cell requires to survive. But, here, perphenazine is restoring the activity of PP2A in the T-ALL cell.”

The researchers are now working to better understand the interactions between PP2A and perphenazine. They also want to search for or develop molecules that bind to and activate the enzyme more tightly and specifically to avoid perphenazine’s psychiatric effects.

“The challenge is to use medicinal chemistry to develop new PP2A inhibitors similar to perphenazine and the other phenothiazines, but to dial down dopamine interactions and accentuate those with PP2A,” said study author A. Thomas Look, MD, also of Dana-Farber.

He added that future PP2A inhibitors could be important additions to the oncologist’s arsenal. When used in combination with other drugs, the inhibitors might “make a real difference” for patients with T-ALL.

The investigators also believe the benefits of PP2A-activating drugs could extend beyond T-ALL.

“The proteins that PP2A suppresses, such as Myc and Akt, are involved in many tumors,” Dr Look noted. “We are optimistic that PP2A activators will have quite broad activity against different kinds of cancer, and we’re anxious to study the pathway in other malignancies as well.”

Genetically modified zebrafish

Experiments in zebrafish have shown that a 50-year-old antipsychotic medication called perphenazine can actively combat T-cell acute lymphoblastic leukemia (T-ALL).

The drug works by turning on a cancer-suppressing enzyme called PP2A and causing malignant tumor cells to self-destruct.

The findings suggest that developing medications that activate PP2A, while avoiding perphenazine’s psychotropic effects, could help clinicians make much-needed headway against T-ALL and perhaps other tumors as well.

Alejandro Gutierrez, MD, of the Dana-Farber Cancer Institute in Boston, and his colleagues detailed this research in The Journal of Clinical Investigation.

The researchers screened a library of 4880 compounds—including FDA-approved drugs whose patents had expired, small molecules, and natural products—in a model of T-ALL engineered using zebrafish.

One of the strongest hits in the zebrafish screen was perphenazine. The drug is a member of the phenothiazines family of antipsychotic medications, which can block dopamine receptors.

The investigators verified perphenazine’s anti-leukemic potential in vitro in several mouse and human T-ALL cell lines. Biochemical studies indicated that perphenazine’s anti-tumor activity is independent of its psychotropic activity and that it attacks T-ALL cells by turning on PP2A.

The fact that perphenazine works by reactivating a protein shut down in cancer cells is novel in the drug development field.

“We rarely find potential drug molecules that activate an enzyme,” Dr Gutierrez explained. “Most new drugs deactivate some protein or signal that the cancer cell requires to survive. But, here, perphenazine is restoring the activity of PP2A in the T-ALL cell.”

The researchers are now working to better understand the interactions between PP2A and perphenazine. They also want to search for or develop molecules that bind to and activate the enzyme more tightly and specifically to avoid perphenazine’s psychiatric effects.

“The challenge is to use medicinal chemistry to develop new PP2A inhibitors similar to perphenazine and the other phenothiazines, but to dial down dopamine interactions and accentuate those with PP2A,” said study author A. Thomas Look, MD, also of Dana-Farber.

He added that future PP2A inhibitors could be important additions to the oncologist’s arsenal. When used in combination with other drugs, the inhibitors might “make a real difference” for patients with T-ALL.

The investigators also believe the benefits of PP2A-activating drugs could extend beyond T-ALL.

“The proteins that PP2A suppresses, such as Myc and Akt, are involved in many tumors,” Dr Look noted. “We are optimistic that PP2A activators will have quite broad activity against different kinds of cancer, and we’re anxious to study the pathway in other malignancies as well.”

NEW ORLEANS – Modified T cells continue to show their mettle against treatment-refractory leukemias, based on study results presented at the annual meeting of the American Society of Hematology.

Among children and young adults with heavily pretreated relapsed or refractory acute lymphoblastic leukemia (ALL), chimeric antigen receptor (CAR) T cells targeted against the CD19 receptor produced complete responses in 10 of 16 patients, including 3 patients with primary, treatment-refractory ALL who had never previously been in remission, reported Dr. Daniel W. Lee III of the National Cancer Institute in Bethesda, Md.

"We were able to clear CNS [central nervous system] leukemia using CAR-T cells alone," Dr. Lee said.

In a second study, CD19-targeted T cells induced molecular remissions in adults with B-lineage ALL refractory to chemotherapy, said Dr. Marco L. Davila from the cellular therapeutics center at Memorial Sloan-Kettering Cancer Center (MSKCC) in New York City.

The immunotherapy produced a complete response (CR) in 12 of 16 patients, and a complete molecular response (CRm) in 12.

Dr. Davila commented that CAR-T cell therapy appears to be a good therapeutic choice for relapsed/refractory B-ALL.

"Especially in light of the data that we see in indolent lymphomas, where the response rates have not been nearly as great, I would speculate that there may be something about this disease that makes it particularly well suited to the second-generation CAR-T cell therapy," he said.

In both studies, therapy with CAR-T cells served as a bridge to stem cell transplantation for several patients.

Different CAR-T flavors

Each research team used its own variation on CAR-T cell therapy. The NCI investigators collected peripheral blood mononuclear cells (PBMCs) from patients via apheresis and used a gamma retrovirus to introduce into effector cells a genetic sequence targeting the CD19 receptor on malignant cells. The NCI version also uses CD28 costimulatory signaling to boost cell-killing effects.

The patients are conditioned with fludarabine and cyclophosphamide, and the treated T-cells are reinfused into the patients 11 days after harvesting.

In the phase I study, 15 patients with relapsed or refractory ALL and 1 with diffuse large B-cell lymphoma were treated. Eight of the patients had undergone at least one hematopoietic stem cell transplant, and all had received total body irradiation. Four had previously received another form of immunotherapy. The patients had to have been at least 100 days post transplant, with no graft-vs.-host disease.

T-cell expansion and transduction was feasible in this heavily pretreated population. All but two patients had an adequate or good expression of CAR-T cells. These patients were treated nonetheless, and one went on to have a minimal-residual disease (MRD) negative response, Dr. Lee noted.

In all, 10 of the patients had complete responses: All of these patients had ALL, and three had never previously achieved a remission. The patient with non-Hodgkin’s lymphoma did not have a significant treatment response.

Of eight patients who were negative for MRD after therapy, six went on to have stem cell transplants, with no unexpected toxicities.

As in other CAR-T cell studies, the chief toxicities seen included grade 4 neutropenia lasting longer than 2 weeks in nine patients, and the cytokine-release syndrome in four patients (grade 3 in two patients and grade 4 in two patients). One patient with the cytokine-release syndrome had cardiac arrest but was successfully resuscitated.

The cytokine-release syndrome was found to be associated with interleukin-6 (IL-6) and could be ameliorated with the IL-6 blocking agent tocilizumab (Actemra). The severity of cytokine-release syndrome did not correlate with tumor burden, the researchers noted.

MSKCC Study

Dr. Davila and his colleagues used a slightly different CAR-T cell construction, also with CD28 costimulation, to treat B-ALL in adults who either had refractory or relapsed disease (MRD-positive) or who were in their first complete remission. Patients who were positive for the Philadelphia chromosome (Ph+) and those who had extramedullary disease, CNS leukemia, or were in relapse after allogeneic stem cell transplant were all eligible.

He presented data on 16 patients with B-ALL with long-term follow-up: 14 patients had a complete response, with an average time to complete response of 24.5 days.

Seven patients in the MSKCC study have gone on to allogeneic stem cell transplants; three patients in complete remission were not eligible for transplant because of medical contraindications, and one additional patient was being evaluated for transplant. There have been no post-transplant relapses to date, with the longest follow-up out to 2 years, Dr. Davila said.

As in the NCI study, the cytokine-release syndrome was a common toxicity. The investigators initially tried to manage it with steroids but found that it came at the cost of lymphotoxicity that caused a marked decline in serum T-cells. They subsequently switched to tocilizumab, which was effective at treating the syndrome without lymphotoxicity.

Dr. Lee’s study was supported by the National Cancer Institute and St. Baldrick’s Foundation. He discussed off-label use of CAR-T cells. Dr. Lee reported having no conflicts of interest. Dr. Davila’s study was supported by MSKCC. He reported having no conflicts of interest.

NEW ORLEANS – Modified T cells continue to show their mettle against treatment-refractory leukemias, based on study results presented at the annual meeting of the American Society of Hematology.

Among children and young adults with heavily pretreated relapsed or refractory acute lymphoblastic leukemia (ALL), chimeric antigen receptor (CAR) T cells targeted against the CD19 receptor produced complete responses in 10 of 16 patients, including 3 patients with primary, treatment-refractory ALL who had never previously been in remission, reported Dr. Daniel W. Lee III of the National Cancer Institute in Bethesda, Md.

"We were able to clear CNS [central nervous system] leukemia using CAR-T cells alone," Dr. Lee said.

In a second study, CD19-targeted T cells induced molecular remissions in adults with B-lineage ALL refractory to chemotherapy, said Dr. Marco L. Davila from the cellular therapeutics center at Memorial Sloan-Kettering Cancer Center (MSKCC) in New York City.

The immunotherapy produced a complete response (CR) in 12 of 16 patients, and a complete molecular response (CRm) in 12.

Dr. Davila commented that CAR-T cell therapy appears to be a good therapeutic choice for relapsed/refractory B-ALL.

"Especially in light of the data that we see in indolent lymphomas, where the response rates have not been nearly as great, I would speculate that there may be something about this disease that makes it particularly well suited to the second-generation CAR-T cell therapy," he said.

In both studies, therapy with CAR-T cells served as a bridge to stem cell transplantation for several patients.

Different CAR-T flavors

Each research team used its own variation on CAR-T cell therapy. The NCI investigators collected peripheral blood mononuclear cells (PBMCs) from patients via apheresis and used a gamma retrovirus to introduce into effector cells a genetic sequence targeting the CD19 receptor on malignant cells. The NCI version also uses CD28 costimulatory signaling to boost cell-killing effects.

The patients are conditioned with fludarabine and cyclophosphamide, and the treated T-cells are reinfused into the patients 11 days after harvesting.

In the phase I study, 15 patients with relapsed or refractory ALL and 1 with diffuse large B-cell lymphoma were treated. Eight of the patients had undergone at least one hematopoietic stem cell transplant, and all had received total body irradiation. Four had previously received another form of immunotherapy. The patients had to have been at least 100 days post transplant, with no graft-vs.-host disease.

T-cell expansion and transduction was feasible in this heavily pretreated population. All but two patients had an adequate or good expression of CAR-T cells. These patients were treated nonetheless, and one went on to have a minimal-residual disease (MRD) negative response, Dr. Lee noted.

In all, 10 of the patients had complete responses: All of these patients had ALL, and three had never previously achieved a remission. The patient with non-Hodgkin’s lymphoma did not have a significant treatment response.

Of eight patients who were negative for MRD after therapy, six went on to have stem cell transplants, with no unexpected toxicities.

As in other CAR-T cell studies, the chief toxicities seen included grade 4 neutropenia lasting longer than 2 weeks in nine patients, and the cytokine-release syndrome in four patients (grade 3 in two patients and grade 4 in two patients). One patient with the cytokine-release syndrome had cardiac arrest but was successfully resuscitated.

The cytokine-release syndrome was found to be associated with interleukin-6 (IL-6) and could be ameliorated with the IL-6 blocking agent tocilizumab (Actemra). The severity of cytokine-release syndrome did not correlate with tumor burden, the researchers noted.

MSKCC Study

Dr. Davila and his colleagues used a slightly different CAR-T cell construction, also with CD28 costimulation, to treat B-ALL in adults who either had refractory or relapsed disease (MRD-positive) or who were in their first complete remission. Patients who were positive for the Philadelphia chromosome (Ph+) and those who had extramedullary disease, CNS leukemia, or were in relapse after allogeneic stem cell transplant were all eligible.

He presented data on 16 patients with B-ALL with long-term follow-up: 14 patients had a complete response, with an average time to complete response of 24.5 days.

Seven patients in the MSKCC study have gone on to allogeneic stem cell transplants; three patients in complete remission were not eligible for transplant because of medical contraindications, and one additional patient was being evaluated for transplant. There have been no post-transplant relapses to date, with the longest follow-up out to 2 years, Dr. Davila said.

As in the NCI study, the cytokine-release syndrome was a common toxicity. The investigators initially tried to manage it with steroids but found that it came at the cost of lymphotoxicity that caused a marked decline in serum T-cells. They subsequently switched to tocilizumab, which was effective at treating the syndrome without lymphotoxicity.

Dr. Lee’s study was supported by the National Cancer Institute and St. Baldrick’s Foundation. He discussed off-label use of CAR-T cells. Dr. Lee reported having no conflicts of interest. Dr. Davila’s study was supported by MSKCC. He reported having no conflicts of interest.

NEW ORLEANS – Modified T cells continue to show their mettle against treatment-refractory leukemias, based on study results presented at the annual meeting of the American Society of Hematology.

Among children and young adults with heavily pretreated relapsed or refractory acute lymphoblastic leukemia (ALL), chimeric antigen receptor (CAR) T cells targeted against the CD19 receptor produced complete responses in 10 of 16 patients, including 3 patients with primary, treatment-refractory ALL who had never previously been in remission, reported Dr. Daniel W. Lee III of the National Cancer Institute in Bethesda, Md.

"We were able to clear CNS [central nervous system] leukemia using CAR-T cells alone," Dr. Lee said.

In a second study, CD19-targeted T cells induced molecular remissions in adults with B-lineage ALL refractory to chemotherapy, said Dr. Marco L. Davila from the cellular therapeutics center at Memorial Sloan-Kettering Cancer Center (MSKCC) in New York City.

The immunotherapy produced a complete response (CR) in 12 of 16 patients, and a complete molecular response (CRm) in 12.

Dr. Davila commented that CAR-T cell therapy appears to be a good therapeutic choice for relapsed/refractory B-ALL.

"Especially in light of the data that we see in indolent lymphomas, where the response rates have not been nearly as great, I would speculate that there may be something about this disease that makes it particularly well suited to the second-generation CAR-T cell therapy," he said.

In both studies, therapy with CAR-T cells served as a bridge to stem cell transplantation for several patients.

Different CAR-T flavors

Each research team used its own variation on CAR-T cell therapy. The NCI investigators collected peripheral blood mononuclear cells (PBMCs) from patients via apheresis and used a gamma retrovirus to introduce into effector cells a genetic sequence targeting the CD19 receptor on malignant cells. The NCI version also uses CD28 costimulatory signaling to boost cell-killing effects.

The patients are conditioned with fludarabine and cyclophosphamide, and the treated T-cells are reinfused into the patients 11 days after harvesting.

In the phase I study, 15 patients with relapsed or refractory ALL and 1 with diffuse large B-cell lymphoma were treated. Eight of the patients had undergone at least one hematopoietic stem cell transplant, and all had received total body irradiation. Four had previously received another form of immunotherapy. The patients had to have been at least 100 days post transplant, with no graft-vs.-host disease.

T-cell expansion and transduction was feasible in this heavily pretreated population. All but two patients had an adequate or good expression of CAR-T cells. These patients were treated nonetheless, and one went on to have a minimal-residual disease (MRD) negative response, Dr. Lee noted.

In all, 10 of the patients had complete responses: All of these patients had ALL, and three had never previously achieved a remission. The patient with non-Hodgkin’s lymphoma did not have a significant treatment response.

Of eight patients who were negative for MRD after therapy, six went on to have stem cell transplants, with no unexpected toxicities.

As in other CAR-T cell studies, the chief toxicities seen included grade 4 neutropenia lasting longer than 2 weeks in nine patients, and the cytokine-release syndrome in four patients (grade 3 in two patients and grade 4 in two patients). One patient with the cytokine-release syndrome had cardiac arrest but was successfully resuscitated.

The cytokine-release syndrome was found to be associated with interleukin-6 (IL-6) and could be ameliorated with the IL-6 blocking agent tocilizumab (Actemra). The severity of cytokine-release syndrome did not correlate with tumor burden, the researchers noted.

MSKCC Study

Dr. Davila and his colleagues used a slightly different CAR-T cell construction, also with CD28 costimulation, to treat B-ALL in adults who either had refractory or relapsed disease (MRD-positive) or who were in their first complete remission. Patients who were positive for the Philadelphia chromosome (Ph+) and those who had extramedullary disease, CNS leukemia, or were in relapse after allogeneic stem cell transplant were all eligible.

He presented data on 16 patients with B-ALL with long-term follow-up: 14 patients had a complete response, with an average time to complete response of 24.5 days.

Seven patients in the MSKCC study have gone on to allogeneic stem cell transplants; three patients in complete remission were not eligible for transplant because of medical contraindications, and one additional patient was being evaluated for transplant. There have been no post-transplant relapses to date, with the longest follow-up out to 2 years, Dr. Davila said.

As in the NCI study, the cytokine-release syndrome was a common toxicity. The investigators initially tried to manage it with steroids but found that it came at the cost of lymphotoxicity that caused a marked decline in serum T-cells. They subsequently switched to tocilizumab, which was effective at treating the syndrome without lymphotoxicity.

Dr. Lee’s study was supported by the National Cancer Institute and St. Baldrick’s Foundation. He discussed off-label use of CAR-T cells. Dr. Lee reported having no conflicts of interest. Dr. Davila’s study was supported by MSKCC. He reported having no conflicts of interest.