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The expression of major histocompatibility complex class II (MHC-II) molecules on tumor cells can predict response to immune checkpoint blockade, and a recent analysis of MHC-II–positive tumor features provided some insight into the evolution of that response.

The analysis, which involved RNA sequencing on 58 patients with anti–programmed cell death-1 (PD-1)–treated melanoma and lung tumors and on a subset of matched pretreatment specimens at acquired resistance, also highlighted the Fc-receptor–like 6 (FCRL6) molecule as a potential novel immunotherapy target, Justin M. Balko, PharmD, PhD, of Vanderbilt University Medical Center, Nashville, Tenn., reported at the ASCO-SITC Clinical Immuno-Oncology Symposium.
 

MHC-II

“MHC-II functions to present class-II restricted antigens to CD4+ T cells, especially T helper cells,” he said, explaining that the expression is typically confined to the professional antigen presenting cell (pAPC) population, but has also previously been shown to be both constitutively and dynamically expressed on tumor cells.

He and his colleagues showed in a 2016 study that MHC-II expression on tumor cells had potential as a biomarker for anti-PD-1 response.

The current study was undertaken to further explore the biological implications of MHC-II expression in tumor cells.

“Importantly here, instead of using mRNA for MHC-II, which could be confounded by other cells in the stroma or microenvironment, we performed immunohistochemistry (IHC) for MHC-II specifically on the tumor compartment within these samples,” Dr. Balko said, noting that he and his colleagues were specifically looking for what was different in gene expression patterns in the MHC-II+ tumor cells.

They compared the gene sets that were enriched in HLA-DR+, or MHC-II+, tumor cells within human tumors with those from melanoma cell lines grown ex vivo in culture (which eliminated any confounding factors of RNA data from contaminating stroma or immune cells), and found substantial gene set overlap.

“These were signatures of innate autoimmunity or inflammation, including those describing allograft rejection gene sets, viral myocarditis, and asthma, suggesting there’s a tumor-intrinsic inflammation signal associated with class II expression on tumor cells,” he said. “We also previously showed in the melanoma data set that HLA-DR expression specifically on tumor cells had a strong association with CD4 infiltrate, and a slightly weaker association with the degree of CD8 infiltration within the tumors.”

Similarly, quantitative immunofluorescence of MHC-II expression in 100 triple negative breast cancer tumors showed that those tumors with HLA-DR or MHC-II expression on tumor cells had a greater degree of CD4 infiltrate than did the negative tumors. CD8 infiltrate was also increased, but enrichment was greater toward the CD4 compartment – an interesting finding given that MHC-II presents antigen to T helper cells, Dr. Balko noted.

Dr. Justin M. Balko of Vanderbilt University Medical Center, Nashville, Tenn.
Dr. Justin M. Balko


A closer look at individual genes that were different between class II–negative and positive tumors showed that LAG-3 mRNA was more enriched in the HLA-DR+ tumors, and also in patients who experienced a significant response to anti-PD-1 therapy.

“We also had a small population of samples that were derived from relapsed specimens,” he said. “We performed IHC within a small subset where we had paired tumors from pre-PD-1 response and relapse [to look at] LAG-3+ lymphocytes in the tumor ... and saw significant enrichment of LAG-3 infiltrate in the relapsed specimens. Importantly, all of these tumors were MHC-II+.”
 

Findings in a mouse model

The functional significance of this was explored using an MHC-II–negative orthotopic model cell line unlikely to induce expression of MHC-II when treated with interferon-gamma in culture; MHC-class-II transactivator (CIITA), the master regulator of MHC-II, was used to transduce the cells, resulting in cells that were “constitutively 100% class II+.”

Immunocompetent mice injected with these cells rejected tumors at a much higher rate, but IHC showed more nonregulatory CD4 cells in mice that did not reject the MHC-II+ tumors, Dr. Balko noted.

Gene expression analysis of the rejection-escaped tumors showed more mRNA for PD-1 and LAG-3, similar to what was seen in the study subjects.

“To see if the effect was truly an increase in PD-1 and LAG-3 on lymphocytes within the tumor microenvironment or in lymphoid tissues, we injected immunocompetent mice with either control or CIITA-positive tumors, and then at 7 days harvested either the contralateral lymph node, the spleen, or the proximal or tumor-draining lymph node,” he said.

This showed increased amounts of LAG-3 and PD-1-positive CD4 and CD8 cells in the tumor-draining lymph node, and more LAG-3 PD-1-positive CD8 cells within the tumor itself.

“To perform a therapeutic study, but also to eliminate any confounding factors of the rejecting mice, we waited 14 days after injection of the tumor cells and only enrolled mice with actively growing tumors. We randomized the mice to treatment with either IgG vehicle control, or anti-PD-1, or the combination of anti-PD1 plus LAG-3, and we had a very substantial [75%] complete response rate in the mice with class II–positive tumors treated with the combined PD-1 and LAG-3,” he said. “Importantly, all of the mice in this study were reinoculated with the [MHC-II–negative] cell line and had complete rejection of any subsequent injection of tumor cells.”

To assess whether any other MHC-II receptors could be expressed in the tumor microenvironment, Dr. Balko and his colleagues turned their attention to the FCRL6 molecule, which has previously been shown to be an MHC-II receptor that is expressed on cytolytic cells.
 

 

 

FCRL6

“[FCRL6] actually has an [immunoreceptor tyrosine-based inhibitory motif] domain in the intracellular portion of the human ortholog, which suggests that it could have some inhibitory function,” Dr. Balko said, adding that it has been shown to be expressed in a substantial proportion of natural killer cells and CD8 cells, and in a minor fraction of CD4+ T cells, which have been described as “cytotoxic CD4 cells.”

An immortalized FCRL6-negative natural killer cell line know as NK-92 was used to test for inhibitory function.

“We co-cultured it with K562 cells, which are a leukemia cell line that is both class I and class II negative; because they have a missing-self signal, the natural killer cells will naturally lyse the K562 cells, which can be measured by chromium release,” he explained.

When MHC-II was reconstituted on K562 cells, the natural killer cells still had effective lysis of the K562 cells, but when FCRL6 was also transduced on the natural killer cells, this interaction was stopped, and there was suppression of cytotoxic activity, or chromium release, in the co-cultures, suggesting that FCRL6 may have a checkpoint-like functionality, he said.

In the melanoma dataset, a look at FLCR6 mRNA in the tumor microenvironment showed that it was also much more highly expressed in HLA-DR–positive tumors and in the relapsed specimens.

In the tumors with paired specimens (three of which were MHC-II positive and three of which were MHC-II negative), IHC for FCRL6 identified greater enrichment of lymphocytes in the MHC-II–positive tumors, but the difference was not statistically significant.

In the breast cancer samples, where more LAG-3 and FCRL6 was seen in the triple-negative breast tumors, quantitative immunofluorescence showed that FCRL6-postive lymphocytes and LAG-3-positive lymphocytes had a substantial suppression of CD8-sel-positive granzyme B-positive cells within the microenvironment that was more substantial than that observed with PD-L1 expression, he noted.

“So our conclusions are that MHC-II tumors demonstrate enhanced T cell-mediated inflammation and immunity and anti-tumor immunity is circumvented through adaptive resistance by PD-1 and potentially LAG-3/MHC-II engagement in some tumors, and that ... FCRL6 may be a novel MHC-II receptor with inhibitory functionality, and could be a new immunotherapy target,” he said.

MHC-II expression could be useful for stratifying patients to combined anti-PD-1/anti-LAG-3 therapy, and eventually to combined anti-PD-1/anti-FCRL6 therapy, he added.
 

Combined anti-PD-1 and anti-LAG-3 therapy

The findings are of particular interest given recent findings regarding LAG-3 antibodies in development, said invited discussant Antoni Ribas, MD.

In a study reported by Ascierto et al. at ASCO 2017, for example, combined anti-PD-1 and anti-LAG-3 therapy had a 13% overall response rate in metastatic melanoma patients who progressed on anti-PD-1 therapy alone (20% and 7.1% in those with and without LAG-3 expression, respectively), said Dr. Ribas of the University of California, Los Angeles.

Dr. Antoni Ribas of the University of California, Los Angeles
Dr. Antoni Ribas


The 20% response rate seen in those with LAG-3 expression suggests “there could be a biomarker for this combined therapy,” he said, noting that while the overall response rate of 13% is low, “it is relevant because it is rescuing some patients who progressed on therapy, and it follows Dr. Balko’s science of why that would be the case.”

Dr. Balko has received research funding from Incyte, and holds a patent on use of HLA-DR/MHC expression to predict response to immunotherapies. Dr. Ribas owns stock in Advaxis, Arcus Ventures, Compugen, CytomX Therapeutics, Five Prime Therapeutics, FLX Bio, and Kite Pharma, and has served as a consultant or adviser for Amgen, Genentech/Roche, Merck, Novartis, and Pierre Fabre.

SOURCE: Balko J et al., ASCO-SITC abstract 180

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The expression of major histocompatibility complex class II (MHC-II) molecules on tumor cells can predict response to immune checkpoint blockade, and a recent analysis of MHC-II–positive tumor features provided some insight into the evolution of that response.

The analysis, which involved RNA sequencing on 58 patients with anti–programmed cell death-1 (PD-1)–treated melanoma and lung tumors and on a subset of matched pretreatment specimens at acquired resistance, also highlighted the Fc-receptor–like 6 (FCRL6) molecule as a potential novel immunotherapy target, Justin M. Balko, PharmD, PhD, of Vanderbilt University Medical Center, Nashville, Tenn., reported at the ASCO-SITC Clinical Immuno-Oncology Symposium.
 

MHC-II

“MHC-II functions to present class-II restricted antigens to CD4+ T cells, especially T helper cells,” he said, explaining that the expression is typically confined to the professional antigen presenting cell (pAPC) population, but has also previously been shown to be both constitutively and dynamically expressed on tumor cells.

He and his colleagues showed in a 2016 study that MHC-II expression on tumor cells had potential as a biomarker for anti-PD-1 response.

The current study was undertaken to further explore the biological implications of MHC-II expression in tumor cells.

“Importantly here, instead of using mRNA for MHC-II, which could be confounded by other cells in the stroma or microenvironment, we performed immunohistochemistry (IHC) for MHC-II specifically on the tumor compartment within these samples,” Dr. Balko said, noting that he and his colleagues were specifically looking for what was different in gene expression patterns in the MHC-II+ tumor cells.

They compared the gene sets that were enriched in HLA-DR+, or MHC-II+, tumor cells within human tumors with those from melanoma cell lines grown ex vivo in culture (which eliminated any confounding factors of RNA data from contaminating stroma or immune cells), and found substantial gene set overlap.

“These were signatures of innate autoimmunity or inflammation, including those describing allograft rejection gene sets, viral myocarditis, and asthma, suggesting there’s a tumor-intrinsic inflammation signal associated with class II expression on tumor cells,” he said. “We also previously showed in the melanoma data set that HLA-DR expression specifically on tumor cells had a strong association with CD4 infiltrate, and a slightly weaker association with the degree of CD8 infiltration within the tumors.”

Similarly, quantitative immunofluorescence of MHC-II expression in 100 triple negative breast cancer tumors showed that those tumors with HLA-DR or MHC-II expression on tumor cells had a greater degree of CD4 infiltrate than did the negative tumors. CD8 infiltrate was also increased, but enrichment was greater toward the CD4 compartment – an interesting finding given that MHC-II presents antigen to T helper cells, Dr. Balko noted.

Dr. Justin M. Balko of Vanderbilt University Medical Center, Nashville, Tenn.
Dr. Justin M. Balko


A closer look at individual genes that were different between class II–negative and positive tumors showed that LAG-3 mRNA was more enriched in the HLA-DR+ tumors, and also in patients who experienced a significant response to anti-PD-1 therapy.

“We also had a small population of samples that were derived from relapsed specimens,” he said. “We performed IHC within a small subset where we had paired tumors from pre-PD-1 response and relapse [to look at] LAG-3+ lymphocytes in the tumor ... and saw significant enrichment of LAG-3 infiltrate in the relapsed specimens. Importantly, all of these tumors were MHC-II+.”
 

Findings in a mouse model

The functional significance of this was explored using an MHC-II–negative orthotopic model cell line unlikely to induce expression of MHC-II when treated with interferon-gamma in culture; MHC-class-II transactivator (CIITA), the master regulator of MHC-II, was used to transduce the cells, resulting in cells that were “constitutively 100% class II+.”

Immunocompetent mice injected with these cells rejected tumors at a much higher rate, but IHC showed more nonregulatory CD4 cells in mice that did not reject the MHC-II+ tumors, Dr. Balko noted.

Gene expression analysis of the rejection-escaped tumors showed more mRNA for PD-1 and LAG-3, similar to what was seen in the study subjects.

“To see if the effect was truly an increase in PD-1 and LAG-3 on lymphocytes within the tumor microenvironment or in lymphoid tissues, we injected immunocompetent mice with either control or CIITA-positive tumors, and then at 7 days harvested either the contralateral lymph node, the spleen, or the proximal or tumor-draining lymph node,” he said.

This showed increased amounts of LAG-3 and PD-1-positive CD4 and CD8 cells in the tumor-draining lymph node, and more LAG-3 PD-1-positive CD8 cells within the tumor itself.

“To perform a therapeutic study, but also to eliminate any confounding factors of the rejecting mice, we waited 14 days after injection of the tumor cells and only enrolled mice with actively growing tumors. We randomized the mice to treatment with either IgG vehicle control, or anti-PD-1, or the combination of anti-PD1 plus LAG-3, and we had a very substantial [75%] complete response rate in the mice with class II–positive tumors treated with the combined PD-1 and LAG-3,” he said. “Importantly, all of the mice in this study were reinoculated with the [MHC-II–negative] cell line and had complete rejection of any subsequent injection of tumor cells.”

To assess whether any other MHC-II receptors could be expressed in the tumor microenvironment, Dr. Balko and his colleagues turned their attention to the FCRL6 molecule, which has previously been shown to be an MHC-II receptor that is expressed on cytolytic cells.
 

 

 

FCRL6

“[FCRL6] actually has an [immunoreceptor tyrosine-based inhibitory motif] domain in the intracellular portion of the human ortholog, which suggests that it could have some inhibitory function,” Dr. Balko said, adding that it has been shown to be expressed in a substantial proportion of natural killer cells and CD8 cells, and in a minor fraction of CD4+ T cells, which have been described as “cytotoxic CD4 cells.”

An immortalized FCRL6-negative natural killer cell line know as NK-92 was used to test for inhibitory function.

“We co-cultured it with K562 cells, which are a leukemia cell line that is both class I and class II negative; because they have a missing-self signal, the natural killer cells will naturally lyse the K562 cells, which can be measured by chromium release,” he explained.

When MHC-II was reconstituted on K562 cells, the natural killer cells still had effective lysis of the K562 cells, but when FCRL6 was also transduced on the natural killer cells, this interaction was stopped, and there was suppression of cytotoxic activity, or chromium release, in the co-cultures, suggesting that FCRL6 may have a checkpoint-like functionality, he said.

In the melanoma dataset, a look at FLCR6 mRNA in the tumor microenvironment showed that it was also much more highly expressed in HLA-DR–positive tumors and in the relapsed specimens.

In the tumors with paired specimens (three of which were MHC-II positive and three of which were MHC-II negative), IHC for FCRL6 identified greater enrichment of lymphocytes in the MHC-II–positive tumors, but the difference was not statistically significant.

In the breast cancer samples, where more LAG-3 and FCRL6 was seen in the triple-negative breast tumors, quantitative immunofluorescence showed that FCRL6-postive lymphocytes and LAG-3-positive lymphocytes had a substantial suppression of CD8-sel-positive granzyme B-positive cells within the microenvironment that was more substantial than that observed with PD-L1 expression, he noted.

“So our conclusions are that MHC-II tumors demonstrate enhanced T cell-mediated inflammation and immunity and anti-tumor immunity is circumvented through adaptive resistance by PD-1 and potentially LAG-3/MHC-II engagement in some tumors, and that ... FCRL6 may be a novel MHC-II receptor with inhibitory functionality, and could be a new immunotherapy target,” he said.

MHC-II expression could be useful for stratifying patients to combined anti-PD-1/anti-LAG-3 therapy, and eventually to combined anti-PD-1/anti-FCRL6 therapy, he added.
 

Combined anti-PD-1 and anti-LAG-3 therapy

The findings are of particular interest given recent findings regarding LAG-3 antibodies in development, said invited discussant Antoni Ribas, MD.

In a study reported by Ascierto et al. at ASCO 2017, for example, combined anti-PD-1 and anti-LAG-3 therapy had a 13% overall response rate in metastatic melanoma patients who progressed on anti-PD-1 therapy alone (20% and 7.1% in those with and without LAG-3 expression, respectively), said Dr. Ribas of the University of California, Los Angeles.

Dr. Antoni Ribas of the University of California, Los Angeles
Dr. Antoni Ribas


The 20% response rate seen in those with LAG-3 expression suggests “there could be a biomarker for this combined therapy,” he said, noting that while the overall response rate of 13% is low, “it is relevant because it is rescuing some patients who progressed on therapy, and it follows Dr. Balko’s science of why that would be the case.”

Dr. Balko has received research funding from Incyte, and holds a patent on use of HLA-DR/MHC expression to predict response to immunotherapies. Dr. Ribas owns stock in Advaxis, Arcus Ventures, Compugen, CytomX Therapeutics, Five Prime Therapeutics, FLX Bio, and Kite Pharma, and has served as a consultant or adviser for Amgen, Genentech/Roche, Merck, Novartis, and Pierre Fabre.

SOURCE: Balko J et al., ASCO-SITC abstract 180

 

The expression of major histocompatibility complex class II (MHC-II) molecules on tumor cells can predict response to immune checkpoint blockade, and a recent analysis of MHC-II–positive tumor features provided some insight into the evolution of that response.

The analysis, which involved RNA sequencing on 58 patients with anti–programmed cell death-1 (PD-1)–treated melanoma and lung tumors and on a subset of matched pretreatment specimens at acquired resistance, also highlighted the Fc-receptor–like 6 (FCRL6) molecule as a potential novel immunotherapy target, Justin M. Balko, PharmD, PhD, of Vanderbilt University Medical Center, Nashville, Tenn., reported at the ASCO-SITC Clinical Immuno-Oncology Symposium.
 

MHC-II

“MHC-II functions to present class-II restricted antigens to CD4+ T cells, especially T helper cells,” he said, explaining that the expression is typically confined to the professional antigen presenting cell (pAPC) population, but has also previously been shown to be both constitutively and dynamically expressed on tumor cells.

He and his colleagues showed in a 2016 study that MHC-II expression on tumor cells had potential as a biomarker for anti-PD-1 response.

The current study was undertaken to further explore the biological implications of MHC-II expression in tumor cells.

“Importantly here, instead of using mRNA for MHC-II, which could be confounded by other cells in the stroma or microenvironment, we performed immunohistochemistry (IHC) for MHC-II specifically on the tumor compartment within these samples,” Dr. Balko said, noting that he and his colleagues were specifically looking for what was different in gene expression patterns in the MHC-II+ tumor cells.

They compared the gene sets that were enriched in HLA-DR+, or MHC-II+, tumor cells within human tumors with those from melanoma cell lines grown ex vivo in culture (which eliminated any confounding factors of RNA data from contaminating stroma or immune cells), and found substantial gene set overlap.

“These were signatures of innate autoimmunity or inflammation, including those describing allograft rejection gene sets, viral myocarditis, and asthma, suggesting there’s a tumor-intrinsic inflammation signal associated with class II expression on tumor cells,” he said. “We also previously showed in the melanoma data set that HLA-DR expression specifically on tumor cells had a strong association with CD4 infiltrate, and a slightly weaker association with the degree of CD8 infiltration within the tumors.”

Similarly, quantitative immunofluorescence of MHC-II expression in 100 triple negative breast cancer tumors showed that those tumors with HLA-DR or MHC-II expression on tumor cells had a greater degree of CD4 infiltrate than did the negative tumors. CD8 infiltrate was also increased, but enrichment was greater toward the CD4 compartment – an interesting finding given that MHC-II presents antigen to T helper cells, Dr. Balko noted.

Dr. Justin M. Balko of Vanderbilt University Medical Center, Nashville, Tenn.
Dr. Justin M. Balko


A closer look at individual genes that were different between class II–negative and positive tumors showed that LAG-3 mRNA was more enriched in the HLA-DR+ tumors, and also in patients who experienced a significant response to anti-PD-1 therapy.

“We also had a small population of samples that were derived from relapsed specimens,” he said. “We performed IHC within a small subset where we had paired tumors from pre-PD-1 response and relapse [to look at] LAG-3+ lymphocytes in the tumor ... and saw significant enrichment of LAG-3 infiltrate in the relapsed specimens. Importantly, all of these tumors were MHC-II+.”
 

Findings in a mouse model

The functional significance of this was explored using an MHC-II–negative orthotopic model cell line unlikely to induce expression of MHC-II when treated with interferon-gamma in culture; MHC-class-II transactivator (CIITA), the master regulator of MHC-II, was used to transduce the cells, resulting in cells that were “constitutively 100% class II+.”

Immunocompetent mice injected with these cells rejected tumors at a much higher rate, but IHC showed more nonregulatory CD4 cells in mice that did not reject the MHC-II+ tumors, Dr. Balko noted.

Gene expression analysis of the rejection-escaped tumors showed more mRNA for PD-1 and LAG-3, similar to what was seen in the study subjects.

“To see if the effect was truly an increase in PD-1 and LAG-3 on lymphocytes within the tumor microenvironment or in lymphoid tissues, we injected immunocompetent mice with either control or CIITA-positive tumors, and then at 7 days harvested either the contralateral lymph node, the spleen, or the proximal or tumor-draining lymph node,” he said.

This showed increased amounts of LAG-3 and PD-1-positive CD4 and CD8 cells in the tumor-draining lymph node, and more LAG-3 PD-1-positive CD8 cells within the tumor itself.

“To perform a therapeutic study, but also to eliminate any confounding factors of the rejecting mice, we waited 14 days after injection of the tumor cells and only enrolled mice with actively growing tumors. We randomized the mice to treatment with either IgG vehicle control, or anti-PD-1, or the combination of anti-PD1 plus LAG-3, and we had a very substantial [75%] complete response rate in the mice with class II–positive tumors treated with the combined PD-1 and LAG-3,” he said. “Importantly, all of the mice in this study were reinoculated with the [MHC-II–negative] cell line and had complete rejection of any subsequent injection of tumor cells.”

To assess whether any other MHC-II receptors could be expressed in the tumor microenvironment, Dr. Balko and his colleagues turned their attention to the FCRL6 molecule, which has previously been shown to be an MHC-II receptor that is expressed on cytolytic cells.
 

 

 

FCRL6

“[FCRL6] actually has an [immunoreceptor tyrosine-based inhibitory motif] domain in the intracellular portion of the human ortholog, which suggests that it could have some inhibitory function,” Dr. Balko said, adding that it has been shown to be expressed in a substantial proportion of natural killer cells and CD8 cells, and in a minor fraction of CD4+ T cells, which have been described as “cytotoxic CD4 cells.”

An immortalized FCRL6-negative natural killer cell line know as NK-92 was used to test for inhibitory function.

“We co-cultured it with K562 cells, which are a leukemia cell line that is both class I and class II negative; because they have a missing-self signal, the natural killer cells will naturally lyse the K562 cells, which can be measured by chromium release,” he explained.

When MHC-II was reconstituted on K562 cells, the natural killer cells still had effective lysis of the K562 cells, but when FCRL6 was also transduced on the natural killer cells, this interaction was stopped, and there was suppression of cytotoxic activity, or chromium release, in the co-cultures, suggesting that FCRL6 may have a checkpoint-like functionality, he said.

In the melanoma dataset, a look at FLCR6 mRNA in the tumor microenvironment showed that it was also much more highly expressed in HLA-DR–positive tumors and in the relapsed specimens.

In the tumors with paired specimens (three of which were MHC-II positive and three of which were MHC-II negative), IHC for FCRL6 identified greater enrichment of lymphocytes in the MHC-II–positive tumors, but the difference was not statistically significant.

In the breast cancer samples, where more LAG-3 and FCRL6 was seen in the triple-negative breast tumors, quantitative immunofluorescence showed that FCRL6-postive lymphocytes and LAG-3-positive lymphocytes had a substantial suppression of CD8-sel-positive granzyme B-positive cells within the microenvironment that was more substantial than that observed with PD-L1 expression, he noted.

“So our conclusions are that MHC-II tumors demonstrate enhanced T cell-mediated inflammation and immunity and anti-tumor immunity is circumvented through adaptive resistance by PD-1 and potentially LAG-3/MHC-II engagement in some tumors, and that ... FCRL6 may be a novel MHC-II receptor with inhibitory functionality, and could be a new immunotherapy target,” he said.

MHC-II expression could be useful for stratifying patients to combined anti-PD-1/anti-LAG-3 therapy, and eventually to combined anti-PD-1/anti-FCRL6 therapy, he added.
 

Combined anti-PD-1 and anti-LAG-3 therapy

The findings are of particular interest given recent findings regarding LAG-3 antibodies in development, said invited discussant Antoni Ribas, MD.

In a study reported by Ascierto et al. at ASCO 2017, for example, combined anti-PD-1 and anti-LAG-3 therapy had a 13% overall response rate in metastatic melanoma patients who progressed on anti-PD-1 therapy alone (20% and 7.1% in those with and without LAG-3 expression, respectively), said Dr. Ribas of the University of California, Los Angeles.

Dr. Antoni Ribas of the University of California, Los Angeles
Dr. Antoni Ribas


The 20% response rate seen in those with LAG-3 expression suggests “there could be a biomarker for this combined therapy,” he said, noting that while the overall response rate of 13% is low, “it is relevant because it is rescuing some patients who progressed on therapy, and it follows Dr. Balko’s science of why that would be the case.”

Dr. Balko has received research funding from Incyte, and holds a patent on use of HLA-DR/MHC expression to predict response to immunotherapies. Dr. Ribas owns stock in Advaxis, Arcus Ventures, Compugen, CytomX Therapeutics, Five Prime Therapeutics, FLX Bio, and Kite Pharma, and has served as a consultant or adviser for Amgen, Genentech/Roche, Merck, Novartis, and Pierre Fabre.

SOURCE: Balko J et al., ASCO-SITC abstract 180

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Key clinical point: MHC-II expression could be useful for stratifying patients to anti-PD-1/anti-LAG-3 and other therapies.

Major finding: The ORR was 75% for class II–positive tumors treated with combined anti-PD-1/anti-LAG-3

Study details: RNA sequencing on 58 patients with anti-PD-1-treated tumors and on matched pretreatment specimens.

Disclosures: Dr. Balko has received research funding from Incyte, and holds a patent on use of HLA-DR/MHC expression to predict response to immunotherapies. Dr. Ribas owns stock in Advaxis, Arcus Ventures, Compugen, CytomX Therapeutics, Five Prime Therapeutics, FLX Bio, and Kite Pharma, and has served as a consultant or adviser for Amgen, Genentech/Roche, Merck, Novartis, and Pierre Fabre.

Source: Balko J et al. ASCO-SITC abstract 180.

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