THE CD47-BLOCKING CANCER IMMUNOTHERAPEUTIC TTI-621 HAS ANTI-TUMOR EFFECTS ACROSS A BROAD RANGE OF HEMATOLOGICAL MALIGNANCIES
(Abstract release date: 05/19/16)
EHA Library. A Uger R. 06/09/16; 132922; E1373
Robert A Uger
Contributions
Contributions
Abstract
Abstract: E1373
Type: Eposter Presentation
Background
CD47 binds to signal-regulatory protein α (SIRPα) on the surface of macrophages and delivers a “do not eat” signal that suppresses phagocytosis. There is strong evidence that many hematological and solid tumors upregulate cell surface expression of CD47 as a means to exploit the CD47-SIRPα pathway and escape macrophage-mediated immune surveillance. Blockade of CD47 using TTI-621, a soluble SIRPα-Fc fusion protein (SIRPαFc), is a promising therapeutic strategy to neutralize the suppressive effects of CD47 and promote the eradication of tumor cells by host macrophages.
Aims
Here we have examined the effect of TTI-621 on human hematological tumor cells in vitro and in vivo.
Methods
Human macrophages were derived from peripheral monocytes of healthy donors. For the in vitro phagocytosis assay, tumor cells were co-cultured with macrophages for two hours in the presence of TTI-621 or control Fc protein. Phagocytosis was assessed by confocal microscopy or flow cytometry. Acute myeloid leukemia (AML) xenografts were performed in NOD.SCID mice. Cells from AML patients were transplanted intra-femorally, and following a three week engraftment period, mice were dosed with 5 mg/kg mouse SIRPαFc or 3.3 mg/kg control Fc protein three times/week for four weeks. AML engraftment was determined by %CD45+CD33+ human cells. Lymphoma xenografts were performed in SHrN mice. Namalwa cells were injected subcutaneously into each flank. Toledo cells were injected in 50% Matrigel. Three days (Nawalma) or 10 days (Toledo) after tumor cell implantation, animals received 10 mg/kg mouse SIRPαFc or 6.75 mg/kg control Fc protein, daily five times/week, for three weeks. Tumor volumes were monitored until they reached the maximum volume of 1500mm3.
Results
We first assessed the ability of TTI-621 to trigger macrophage-mediated phagocytosis of cancer cells. In cultures left untreated or treated with a control Fc fragment, macrophages exhibited a low level of phagocytosis, consistent with CD47-mediated suppression. Blockade of CD47 by TTI-621 led to a dramatic increase in the phagocytosis of human tumor cell lines of both myeloid and lymphoid origin, including non-Hodgkin lymphoma lines. Furthermore, TTI-621 enhanced macrophage-mediated phagocytosis of primary tumor samples from patients with AML, myelodysplastic syndrome, multiple myeloma and B- and T-cell acute lymphoblastic leukemia. In total, 77% (23/30) of cell lines and 97% (32/33) of primary patient samples were readily phagocytosed following treatment with TTI-621. We next evaluated the in vivo efficacy of a mouse surrogate of TTI-621 in an AML xenograft model. Treatment of mice with mouse SIRPαFc for four weeks significantly reduced the tumor burden in the injected femur of 7/10 patient samples compared to a control Fc protein, while dramatically reducing the tumor burden in non-injected bone marrow in all 10 AML patient samples. Finally, we assessed the in vivo activity of mouse SIRPαFc in xenograft models of Burkitt lymphoma (Namalwa) and diffuse large B cell lymphoma (Toledo). Treatment with SIRPαFc ablated the growth of Namalwa and Toledo tumors and was superior to rituximab therapy in both models.
Conclusion
Collectively, these data indicate that TTI-621 is active across a broad range of human hematological tumors. A Phase I clinical trial of TTI-621 in patients with advanced hematological malignancies is currently underway (ClinicalTrials.gov #NCT02663518).
Session topic: E-poster
Keyword(s): AML, Immune therapy, Lymphoma therapy, Macrophage
Type: Eposter Presentation
Background
CD47 binds to signal-regulatory protein α (SIRPα) on the surface of macrophages and delivers a “do not eat” signal that suppresses phagocytosis. There is strong evidence that many hematological and solid tumors upregulate cell surface expression of CD47 as a means to exploit the CD47-SIRPα pathway and escape macrophage-mediated immune surveillance. Blockade of CD47 using TTI-621, a soluble SIRPα-Fc fusion protein (SIRPαFc), is a promising therapeutic strategy to neutralize the suppressive effects of CD47 and promote the eradication of tumor cells by host macrophages.
Aims
Here we have examined the effect of TTI-621 on human hematological tumor cells in vitro and in vivo.
Methods
Human macrophages were derived from peripheral monocytes of healthy donors. For the in vitro phagocytosis assay, tumor cells were co-cultured with macrophages for two hours in the presence of TTI-621 or control Fc protein. Phagocytosis was assessed by confocal microscopy or flow cytometry. Acute myeloid leukemia (AML) xenografts were performed in NOD.SCID mice. Cells from AML patients were transplanted intra-femorally, and following a three week engraftment period, mice were dosed with 5 mg/kg mouse SIRPαFc or 3.3 mg/kg control Fc protein three times/week for four weeks. AML engraftment was determined by %CD45+CD33+ human cells. Lymphoma xenografts were performed in SHrN mice. Namalwa cells were injected subcutaneously into each flank. Toledo cells were injected in 50% Matrigel. Three days (Nawalma) or 10 days (Toledo) after tumor cell implantation, animals received 10 mg/kg mouse SIRPαFc or 6.75 mg/kg control Fc protein, daily five times/week, for three weeks. Tumor volumes were monitored until they reached the maximum volume of 1500mm3.
Results
We first assessed the ability of TTI-621 to trigger macrophage-mediated phagocytosis of cancer cells. In cultures left untreated or treated with a control Fc fragment, macrophages exhibited a low level of phagocytosis, consistent with CD47-mediated suppression. Blockade of CD47 by TTI-621 led to a dramatic increase in the phagocytosis of human tumor cell lines of both myeloid and lymphoid origin, including non-Hodgkin lymphoma lines. Furthermore, TTI-621 enhanced macrophage-mediated phagocytosis of primary tumor samples from patients with AML, myelodysplastic syndrome, multiple myeloma and B- and T-cell acute lymphoblastic leukemia. In total, 77% (23/30) of cell lines and 97% (32/33) of primary patient samples were readily phagocytosed following treatment with TTI-621. We next evaluated the in vivo efficacy of a mouse surrogate of TTI-621 in an AML xenograft model. Treatment of mice with mouse SIRPαFc for four weeks significantly reduced the tumor burden in the injected femur of 7/10 patient samples compared to a control Fc protein, while dramatically reducing the tumor burden in non-injected bone marrow in all 10 AML patient samples. Finally, we assessed the in vivo activity of mouse SIRPαFc in xenograft models of Burkitt lymphoma (Namalwa) and diffuse large B cell lymphoma (Toledo). Treatment with SIRPαFc ablated the growth of Namalwa and Toledo tumors and was superior to rituximab therapy in both models.
Conclusion
Collectively, these data indicate that TTI-621 is active across a broad range of human hematological tumors. A Phase I clinical trial of TTI-621 in patients with advanced hematological malignancies is currently underway (ClinicalTrials.gov #NCT02663518).
Session topic: E-poster
Keyword(s): AML, Immune therapy, Lymphoma therapy, Macrophage
Abstract: E1373
Type: Eposter Presentation
Background
CD47 binds to signal-regulatory protein α (SIRPα) on the surface of macrophages and delivers a “do not eat” signal that suppresses phagocytosis. There is strong evidence that many hematological and solid tumors upregulate cell surface expression of CD47 as a means to exploit the CD47-SIRPα pathway and escape macrophage-mediated immune surveillance. Blockade of CD47 using TTI-621, a soluble SIRPα-Fc fusion protein (SIRPαFc), is a promising therapeutic strategy to neutralize the suppressive effects of CD47 and promote the eradication of tumor cells by host macrophages.
Aims
Here we have examined the effect of TTI-621 on human hematological tumor cells in vitro and in vivo.
Methods
Human macrophages were derived from peripheral monocytes of healthy donors. For the in vitro phagocytosis assay, tumor cells were co-cultured with macrophages for two hours in the presence of TTI-621 or control Fc protein. Phagocytosis was assessed by confocal microscopy or flow cytometry. Acute myeloid leukemia (AML) xenografts were performed in NOD.SCID mice. Cells from AML patients were transplanted intra-femorally, and following a three week engraftment period, mice were dosed with 5 mg/kg mouse SIRPαFc or 3.3 mg/kg control Fc protein three times/week for four weeks. AML engraftment was determined by %CD45+CD33+ human cells. Lymphoma xenografts were performed in SHrN mice. Namalwa cells were injected subcutaneously into each flank. Toledo cells were injected in 50% Matrigel. Three days (Nawalma) or 10 days (Toledo) after tumor cell implantation, animals received 10 mg/kg mouse SIRPαFc or 6.75 mg/kg control Fc protein, daily five times/week, for three weeks. Tumor volumes were monitored until they reached the maximum volume of 1500mm3.
Results
We first assessed the ability of TTI-621 to trigger macrophage-mediated phagocytosis of cancer cells. In cultures left untreated or treated with a control Fc fragment, macrophages exhibited a low level of phagocytosis, consistent with CD47-mediated suppression. Blockade of CD47 by TTI-621 led to a dramatic increase in the phagocytosis of human tumor cell lines of both myeloid and lymphoid origin, including non-Hodgkin lymphoma lines. Furthermore, TTI-621 enhanced macrophage-mediated phagocytosis of primary tumor samples from patients with AML, myelodysplastic syndrome, multiple myeloma and B- and T-cell acute lymphoblastic leukemia. In total, 77% (23/30) of cell lines and 97% (32/33) of primary patient samples were readily phagocytosed following treatment with TTI-621. We next evaluated the in vivo efficacy of a mouse surrogate of TTI-621 in an AML xenograft model. Treatment of mice with mouse SIRPαFc for four weeks significantly reduced the tumor burden in the injected femur of 7/10 patient samples compared to a control Fc protein, while dramatically reducing the tumor burden in non-injected bone marrow in all 10 AML patient samples. Finally, we assessed the in vivo activity of mouse SIRPαFc in xenograft models of Burkitt lymphoma (Namalwa) and diffuse large B cell lymphoma (Toledo). Treatment with SIRPαFc ablated the growth of Namalwa and Toledo tumors and was superior to rituximab therapy in both models.
Conclusion
Collectively, these data indicate that TTI-621 is active across a broad range of human hematological tumors. A Phase I clinical trial of TTI-621 in patients with advanced hematological malignancies is currently underway (ClinicalTrials.gov #NCT02663518).
Session topic: E-poster
Keyword(s): AML, Immune therapy, Lymphoma therapy, Macrophage
Type: Eposter Presentation
Background
CD47 binds to signal-regulatory protein α (SIRPα) on the surface of macrophages and delivers a “do not eat” signal that suppresses phagocytosis. There is strong evidence that many hematological and solid tumors upregulate cell surface expression of CD47 as a means to exploit the CD47-SIRPα pathway and escape macrophage-mediated immune surveillance. Blockade of CD47 using TTI-621, a soluble SIRPα-Fc fusion protein (SIRPαFc), is a promising therapeutic strategy to neutralize the suppressive effects of CD47 and promote the eradication of tumor cells by host macrophages.
Aims
Here we have examined the effect of TTI-621 on human hematological tumor cells in vitro and in vivo.
Methods
Human macrophages were derived from peripheral monocytes of healthy donors. For the in vitro phagocytosis assay, tumor cells were co-cultured with macrophages for two hours in the presence of TTI-621 or control Fc protein. Phagocytosis was assessed by confocal microscopy or flow cytometry. Acute myeloid leukemia (AML) xenografts were performed in NOD.SCID mice. Cells from AML patients were transplanted intra-femorally, and following a three week engraftment period, mice were dosed with 5 mg/kg mouse SIRPαFc or 3.3 mg/kg control Fc protein three times/week for four weeks. AML engraftment was determined by %CD45+CD33+ human cells. Lymphoma xenografts were performed in SHrN mice. Namalwa cells were injected subcutaneously into each flank. Toledo cells were injected in 50% Matrigel. Three days (Nawalma) or 10 days (Toledo) after tumor cell implantation, animals received 10 mg/kg mouse SIRPαFc or 6.75 mg/kg control Fc protein, daily five times/week, for three weeks. Tumor volumes were monitored until they reached the maximum volume of 1500mm3.
Results
We first assessed the ability of TTI-621 to trigger macrophage-mediated phagocytosis of cancer cells. In cultures left untreated or treated with a control Fc fragment, macrophages exhibited a low level of phagocytosis, consistent with CD47-mediated suppression. Blockade of CD47 by TTI-621 led to a dramatic increase in the phagocytosis of human tumor cell lines of both myeloid and lymphoid origin, including non-Hodgkin lymphoma lines. Furthermore, TTI-621 enhanced macrophage-mediated phagocytosis of primary tumor samples from patients with AML, myelodysplastic syndrome, multiple myeloma and B- and T-cell acute lymphoblastic leukemia. In total, 77% (23/30) of cell lines and 97% (32/33) of primary patient samples were readily phagocytosed following treatment with TTI-621. We next evaluated the in vivo efficacy of a mouse surrogate of TTI-621 in an AML xenograft model. Treatment of mice with mouse SIRPαFc for four weeks significantly reduced the tumor burden in the injected femur of 7/10 patient samples compared to a control Fc protein, while dramatically reducing the tumor burden in non-injected bone marrow in all 10 AML patient samples. Finally, we assessed the in vivo activity of mouse SIRPαFc in xenograft models of Burkitt lymphoma (Namalwa) and diffuse large B cell lymphoma (Toledo). Treatment with SIRPαFc ablated the growth of Namalwa and Toledo tumors and was superior to rituximab therapy in both models.
Conclusion
Collectively, these data indicate that TTI-621 is active across a broad range of human hematological tumors. A Phase I clinical trial of TTI-621 in patients with advanced hematological malignancies is currently underway (ClinicalTrials.gov #NCT02663518).
Session topic: E-poster
Keyword(s): AML, Immune therapy, Lymphoma therapy, Macrophage
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