356 Personalized immunotherapy by adoptive T cell transfer during chemotherapy with or without interferon-alpha in patients with recurrent platinum-sensitive epithelial ovarian cancer

Background

Epithelial ovarian cancer (EOC) is considered an immunogenic tumor, as illustrated by the clear correlation between T-cell infiltration and overall survival. This suggests that patients with EOC may be eligible for immunotherapy including adoptive cell therapy with autologous Tumor Infiltrating Lymphocytes (TIL). However, immunosuppressive cells including myeloid derived suppressor cells an regulatory T cells are also abundant in EOC and may need to be targeted simultaneously to achieve the full potential of the infused TIL. Carboplatin-paclitaxel chemotherapy (CPC) reduces the number of immunosuppressive cells in cervical cancer patients,1 creating a window-of-opportunity for TIL to exert their full effector function. Interferon-alpha further supports infused TIL. A phase I/II trial (NCT04072263) was initiated to study the feasibility and safety of TIL during CPC with or without additional interferon-alpha in patients with recurrent platinum-sensitive EOC.

Methods

Fifteen patients with recurrent platinum-sensitive EOC received 6 cycles of CPC intravenously every 3 weeks and TIL intravenously 2 weeks after the 2nd,3rd and 4th CPC cycle. Pegylated-interferon-alpha was added in the second cohort for 12 weeks, starting one week before the first TIL infusion. Patients who received 3 TIL infusions were evaluable. The primary endpoint was feasibility and safety of TIL administration during CPC with or without interferon-alpha. As secondary endpoints signs of activity, underlying mechanisms, immunomodulation, and T-cell reactivity were studied.

Results

Thirteen patients were available for analysis. Median age 63 years (range, 29–77). TIL could be successfully expanded for all patients. Treatment with TIL during CPC was safe and did not add toxicity. Addition of IFNα resulted in grade 3 leucopenia and grade 3 trombocytopenia in the first 2 patients and was therefore omitted in subsequent patients. CPC alleviated the immunosuppressive status, reflected by reduced plasma IL-6 levels and circulating myeloid-cell numbers, while lymphocytes numbers are not affected. This was most prominently at 1–2 weeks after the 2nd CPC and is suggested to reflect improved conditions promoting intra-tumoral T-cell reactivity. Objective responses were observed in 10/13 (77%) patients and 3 patients had stable disease. Interestingly, in at least one patient the ongoing platinum-free interval of 25 months far exceeds the first platinum-free interval of 8 months after similar CPC. In depth studies on immune modulation by chemotherapy and by TIL/Interferon-alpha, and correlations between TIL phenotype and clinical outcome are ongoing and will be presented.

Conclusions

Combined treatment with CP chemotherapy and properly timed TIL may result in clinical benefit for patients with EOC.

Acknowledgements

The unrestricted funding of the trial by Ovacure is greatly acknowledged.

Trial Registration

The trial is registered at www.clinicaltrials.gov under number NCT04072263.

Reference

Welters MJ, van der Sluis TC, van Meir H, Loof NM, van Ham VJ, van Duikeren S, Santegoets SJ, Arens R, de Kam ML, Cohen AF, van Poelgeest MI, Kenter GG, Kroep JR, Burggraaf J, Melief CJ, van der Burg SH. Vaccination during myeloid cell depletion by cancer chemotherapy fosters robust T cell responses. Sci Transl Med 2016;8(334):334ra52. doi: 10.1126/scitranslmed.aad8307

Ethics Approval

This study was approved by Leiden University Medical Center‘s Ethics Board; approval number L18-012 and the Central Committee on Research Involving Human Subjects; approval number NL63434.000.17.

Low-dose interferon-alpha preconditioning and adoptive cell therapy in patients with metastatic melanoma refractory to standard (immune) therapies: a phase I/II study

BACKGROUND

Adoptive cell therapy (ACT) with tumor-reactive T cells has shown consistent clinical efficacy. We evaluated the response to ACT in combination with interferon alpha (IFNa) preconditioning in patients with stage IV metastatic melanoma, most of which were progressive on cytotoxic T-lymphocyte-associated protein 4 and/or programmed cell death protein 1 checkpoint blockade therapy.

METHODS

Thirty-four patients were treated with ex vivo expanded tumor reactive T cells, derived from mixed lymphocyte autologous tumor cultures, or with autologous tumor-infiltrating lymphocytes and evaluated for clinical response. Clinical and immunological parameters associated with response were also evaluated.

RESULTS

Best overall response defined as clinical benefit, comprising either complete response, partial response or stable disease >6 months, was observed in 29% of the patients. Forty-three per cent of the 14 immunotherapy-naïve patients and 20% of the 20 patients progressive on prior immunotherapy benefited from ACT. The overall survival (OS) was 90% versus 28.6% at 1 year and 46.7% versus 0% at 3 years follow-up, of responder and non-responder patients, respectively. Median OS was 36 versus 7 months, respectively. IFNa pretreatment resulted in leukopenia, neutropenia and lymphopenia, which was sustained during the treatment in clinical responders and associated with response. Differences in antigen specificity, but not in phenotype, cytokine profile or CD8+ T cell number of the ACT products correlated with clinical response. Cross-reactivity of the ACT products to one or more allogeneic human leukocyte antigen-matched melanoma cell lines was associated with short OS after treatment while the ACT products of very long-term survivors showed no cross-reactivity but recognized patient-specific neoantigens.

CONCLUSION

This study demonstrates that ACT in combination with a mild IFNa preconditioning regimen can induce clinical benefit even in immunotherapy pretreated patients, although with lower success than in immunotherapy-naïve patients. ACT products comprising neoantigen reactivity may be more effective.

Abstract 542: T-cell engager bispecific formats of an AML patient-derived antibody targeting a unique sialylated CD43 epitope induce kill of melanoma cells in vitro and in vivo

Introduction CD43s, a unique sialylated form of CD43 expressed by myeloid malignancies, is a novel target and AT1413, an antibody targeting CD43s was shown to have therapeutic potential against acute myeloid leukemia (AML) and myelodysplastic syndrome. CD43s is recognized by the human antibody AT1413, that was isolated from a high-risk AML patient who successfully cleared the leukemia after allogeneic stem cell transplantation. Because CD43 is also expressed in non-hematopoietic cells we studied whether CD43s is also present and can also be targeted on non-hematopoietic tumors.

Materials and methods AT1413 binding on a panel of tumor cell lines was analyzed by flow cytometry. AT1413 was constructed into a bispecific T-cell engaging format (AT1413 bTCE) by linking the full-length AT1413 IgG to two single chain variable fragments against CD3ϵ with a combination of site-specific enzymatic and chemical coupling. A monovalent T-cell engager was produced as heterotrimer consisting of one AT1413 monovalent chain and one anti-CD3 scFV fused to AT1413 monovalent chain. Point mutations in the IgG heavy chain were introduced to prevent interactions between AT1413 T-cell engagers and Fc-receptors. The cytotoxicity-inducing activities were established using PBMCs as effector and tumor cells as target cells using standard cytotoxic assays in vitro and in vivo in a mouse model carrying human immune cells.

Results We observed that AT1413 binds to non-hematopoietic tumor cells, such as melanoma and breast cancer. AT1413 immune precipitated CD43s from melanoma cells confirming that it recognizes the same target on melanoma as on AML. AT1413 induced antibody dependent cellular cytotoxicity against melanoma cell lines and primary melanoma samples. However, AT1413 was unable to affect growth of melanoma cells in vivo. To increase the efficacy of AT1413 it was formatted as a bispecific T-cell engaging antibody (TCE): one binding bivalently (bTCE) to CD43s and monovalently to CD3ϵ and the other monovalently (KiH) to both CD43s and CD3ϵ. In vitro, these TCEs redirected T-cell cytotoxicity against melanoma cells with different potencies. To investigate their effects in vivo, we grafted mice that harbor a human immune system with the melanoma cell line A375. Treatment with both AT1413 bTCE and AT1413 KiH significantly reduced tumor outgrowth.

Conclusion AT1413 recognizes a sialylated epitope on CD43 shared by melanoma, AML and MDS cells. Two different bispecific TCE forms of AT1413 induce strong anti-tumor cytotoxic activities in vitro and in vivo. These data indicate a broad therapeutic potential of AT1413.

Citation Format: Greta de Jong, Lina Bartels, Martijn Kedde, Els Verdegaal, Marijn A. Gillissen, Sophie E. Levie, Madalina G. Cercel, Susan E. van Hal-van Veen, Christien Fatmawati, Dorien van de Berg, Etsuko Yasuda, Yvonne Claassen, Arjen Q. Bakker, Remko Schotte, Julien Villaudy, Koen Wagner, Hergen Spits, Mette D. Hazenberg, Pauline M. van Helden. T-cell engager bispecific formats of an AML patient-derived antibody targeting a unique sialylated CD43 epitope induce kill of melanoma cells in vitro and in vivo [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 542.

Abstract 531: AT1412, a patient-derived antibody in development for the treatment of CD9-positive precursor B-acute lymphoblastic leukemia

Introduction

Despite rapid advances in immunotherapeutic options for precursor B-acute lymphoblastic leukemia (BCP-ALL), outcomes remain poor especially for adult ALL and relapsed pediatric ALL. With conventional chemotherapy remission percentages in adult ALL range from 75 to 90%, but relapse rates are high and long-term leukemia-free survival ranges between 35-70% depending on age and risk group. The introduction of CD19-targeting immunotherapy has significantly improved patient outcomes in (relapsed) BCP-ALL. However, tumor escape via downregulation of CD19 occurs in a significant number of patients. An ongoing medical need remains for the identification of alternative immunotherapeutic targets for treatment of ALL.

Methods

CD9 is expressed in 60-80% of BCP-ALL, is correlated with adverse prognosis and has been proposed as therapeutic target for BCP-ALL. AT1412 is a fully human CD9-targeting antibody, that was identified from a patient cured of metastatic melanoma after adoptive T-cell therapy, using our B-cell immortalization technology (AIMSelect) [Kwakkenbos et al. Nat. Med. 2010]. The antibody was selected based on differential binding to melanoma cells as compared to healthy melanocytes and was shown to be successful in killing melanoma cells in vitro and in vivo.

Results

Binding of AT1412 to BCP-ALL cell lines SUP-B15, MHH-CALL-2 and CCRF-SB varied as expected based on CD9 levels that we detected using a commercial CD9 antibody. AT1412-induced antibody dependent cellular cytotoxicity (ADCC) and antibody dependent cellular phagocytosis (ADCP) correlated with the level of AT1412 binding. No binding was seen to the T-ALL cell line Jurkat. These findings were confirmed in primary ALL samples, obtained prospectively at diagnosis from a cohort of patients with T- or B-ALL (n=38). AT1412 showed binding to the majority of B-ALL samples but not to T-ALL samples. AT1412 induced ADCC of nearly all B-ALL samples it bound to (10/11) and of none of the non-binding B-ALL or T-ALL samples. Cytotoxicity significantly correlated with the level of AT1412 binding. These findings were corroborated by the observation that AT1412 induced specific B-ALL cell death when a bone marrow sample from a newly diagnosed BCP-ALL patient was incubated with AT1412. Remarkably, AT1412 induced cell death in the absence of added effector cells or other (chemo)therapeutic agents, while the sample contained over 80% blasts and as little as 3% lymphocytes. We are currently investigating the in vivo efficacy of the antibody in a humanized immune system mouse model with human BCP-ALL.

Conclusion

Taken together, the majority of BCP-ALL express CD9 and this is associated with poor prognosis. Our data demonstrate that CD9 can be successfully targeted by the human CD9 antibody AT1412, suggesting that AT1412 has the potential to be developed as a therapeutic antibody for B-ALL. AT1412 is currently being advanced through preclinical development.

Citation Format: Greta de Jong, Sophie E. Levie, Remko Schotte, Wouter Pos, Daniel Go, Etsuko Yasuda, Madalina Cercel, Susan E. van Hal, Esmay Frankin, Aniko Szabo, Martijn Kedde, Els Verdegaal, Julien Villaudy, Sjoerd van der Burg, Pauline M. van Helden, Hans van Eenennaam, Hergen Spits, Anita van Rijneveld, Mette D. Hazenberg. AT1412, a patient-derived antibody in development for the treatment of CD9-positive precursor B-acute lymphoblastic leukemia [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 531.

Abstract 532: A patient-derived anti-CD9 antibody induces tumor rejection and synergistically enhances anti-PD1 activity

Background

Adaptive immunity to cancer cells has been shown to form a crucial part of cancer immunotherapy. Recently, the importance of tumor B-cell signatures were shown to correlate with melanoma survival. We investigated whether anti-tumor antibodies could be isolated from a patient with metastatic melanoma that was tumor-free for 6 years following adoptive transfer of ex vivo expanded autologous T cells (Verdegaal 2011).

Methods

Peripheral blood memory B cells were immortalized using AIMM's immmortalisation technology (ectopic Bcl-6 and Bcl-xL; Kwakkenbos 2010) expression and analyzed for the presence of tumor-reactive B cells.

Results

AT1412 antibody was identified by virtue of its differential binding to melanoma cells as compared to healthy melanocytes. AT1412 was found to bind the tetraspanin CD9, a broadly expressed protein involved in multiple cellular activities and disease progression. The crystal structure of the CD9 large extracellular loop in complex with an AT1412 Fab fragment revealed that AT1412 binds the CD9 epitope in an extended and unfolded conformation. In addition to melanoma, AT1412 binds other tumor types including gastric, colon- and pancreatic cancer. AT1412 was shown to induce antibody dependent cellular cytotoxicity (ADCC) and antibody dependent cellular phagocytosis (ADCP) of cancer cells. In addition, AT1412 demonstrated activation of monocytes, most likely via activation of CD9 on platelets-bound monocytes. In mice carrying a human immune system (HIS-mice; van Lent 2010) AT1412 strongly enhanced tumor rejection of A375 and SKMEL-5 tumor cells. AT1412 treatment was shown to enhance tumor infiltration of CD8 T cells and macrophages. AT1412 efficacy was further synergistically enhanced when combined with an anti-PD1 antibody (nivolumab). Other groups have shown that anti-CD9 antibodies can induce tumor rejection in mice. However, these antibodies could not be advanced due to induction of platelet aggregation. We show that AT1412 does not induce aggregation of both human and cynomolgus platelets. Also affinity matured versions of AT1412 do not induce platelet aggregation, supporting that AT1412 binds a unique epitope on CD9. In addition, we studied the safety of AT1412 during a one month exposure in a weekly administration in cynomolgus monkeys. Besides a transient thrombocytopenia AT1412 was well tolerated up to 10 mg/kg antibody (highest dose tested) and did not lead to other adverse events nor were any coagulation factors affected

Conclusions

Taken together, applying AIMM's proprietary B-cell immortalization technology we isolated antibody AT1412 that targets a unique epitope on CD9. AT1412 was shown to induce tumor rejection as a single agent and enhances the activity of anti-PD-1 antibodies, while not inducing platelet aggregation. One month exposure of AT1412 in monkeys indicated that AT1412 can be safely administered. Preclinical development of AT1412 is ongoing to initiate clinical evaluation in 2020.

Funding

Dutch Cancer Society, grant UVA 2010-4822

Citation Format: Remko Schotte, Julien Villaudy, Martijn Kedde, Wouter Pos, Koen Wagner, Viviana Neviani, Daniel Go, Etsuko Yasuda, Christien Fatmawati, Els Verdegaal, Susan van Hal, Yvonne Claasen, Hans van Eenennaam, Pauline van Helden, Piet Gros, Sjoerd van der Burg, Hergen Spits. A patient-derived anti-CD9 antibody induces tumor rejection and synergistically enhances anti-PD1 activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 532.

Abstract LB-200: A patient derived antibody targeting the tetraspanin CD9 synergistically inhibits tumor growth with an anti PD1 antibody

Background. It is generally accepted that immune reactions against cancer cells can be induced by immunotherapy. Here, we investigated the possibility that an antibody response has contributed to the success of the immunotherapy of a cancer patient.

Methods. A patient with metastatic melanoma was successfully treated by adoptive transfer of ex vivo expanded autologous tumor reactive T cells1. This patient is still tumor free 9 years after treatment. Peripheral blood memory B cells were immortalized by ectopic Bcl-6 and Bcl-xL expression2 and analyzed for the presence of tumor-reactive B cells.

Results. We isolated one B cell clone that produced an antibody, named AT1412, recognizing a novel cell surface epitope on the tetraspanin CD9 which is broadly expressed and involved in multiple cellular activities including proliferation and adherence.

AT1412 bound more strongly to melanoma cells than to melanocytes and other healthy tissues indicating that the AT1412 epitope is overexpressed on tumor cells. In addition, AT1412 strongly reacted with other tumor types including colon, pancreas and, breast cancer. Further analysis revealed that AT1412 favors binding to a clustered state of CD9. CD9 clusters are dependent on palmitoylation and known to be present on metastatic cells3.

Previously published high affinity mouse antibodies targeting human CD9 were found to trigger aggregation of platelets and thus unfit for therapeutic use4. In sharp contrast, AT1412 does not induce platelet aggregation. To address whether AT1412 fails to aggregate platelets because of its low affinity for CD9 we generated high affinity variants of AT1412 using our highly efficient affinity maturation platform. We obtained AT1412 variants with affinities up to 250 fold higher than the wild type AT1412 comparable to that of mouse anti-human CD9 antibodies. These high affinity variants still did not aggregate platelets indicating that the absence of platelet aggregation by AT1412 is due to the spatial arrangement of the AT1412 epitope present on CD9 and not its low affinity.

The antibody was able to reduce growth of melanoma tumors and block metastasis in melanoma xenografted mice. A striking synergistic inhibition of tumor growth was observed in mice that were treated with our CD9 antibody in the presence of a clinically successful anti-PD1 checkpoint inhibitor antibody.

Discussion. These data suggest that the antibody contributed to the success of the immunotherapy in this patient. This antibody could act together with tumor-reactive T cells in eradicating circulating tumor cells and/or preventing settlement of metastatic tumor cells. Importantly, no antibody-related adverse effects were observed during and after treatment of this patient indicating that the antibody is safe for use in humans.

1.

Verdegaal, Cancer Immunol Immunother, 2011

2.

Kwakkenbos, Nat Med, 2010

3.

Yang, JBC, 2006

4.

Boucheix, FEBS Letter, 1983

Citation Format: Remko Schotte, Pauline van Helden, Daniel Go, Christien Fatmawati, Els Verdegaal, Camile Bru, Julien Villaudy, Koen Wagner, Sjoerd van der Burg, Hergen Spits, Wouter Pos. A patient derived antibody targeting the tetraspanin CD9 synergistically inhibits tumor growth with an anti PD1 antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-200. doi:10.1158/1538-7445.AM2017-LB-200

Antagonistic TSC22D1 variants control BRAF(E600)-induced senescence

Oncogene-induced cellular senescence (OIS) is an increasingly recognized tumour suppressor mechanism that confines the outgrowth of neoplastic cells in vivo. It relies on a complex signalling network, but only few components have been identified so far. Gene-expression profiling revealed a >100-fold increase in the levels of the transcription factor and putative tumour suppressor gene TGFβ-stimulated clone 22 (TSC22D1) in BRAF(E600)-induced senescence, in both human fibroblasts and melanocytes. Only the short TSC22D1 transcript was upregulated, whereas the abundance of the large protein variant was suppressed by proteasomal degradation. The TSC22D1 protein variants, in complex with their dimerization partner TSC22 homologue gene 1 (THG1), exerted opposing functions, as selective depletion of the short form, or conversely, overexpression of the large variant, resulted in abrogation of OIS. This was accompanied by the suppression of several inflammatory factors and p15(INK4B), with TSC22D1 acting as a critical effector of C/EBPβ. Our results demonstrate that the differential regulation of antagonistic TSC22D1 variants is required for the establishment of OIS and suggest distinct contributions of TSC22 family members to the progression of BRAF(E600)-driven neoplasia.

Preclinical evaluation of DISC-GMCSF for the treatment of breast carcinoma

BACKGROUND

DISC-hGMCSF is a gH-deleted HSV-2 based vector expressing human GM-CSF that has entered clinical trials for the therapy of metastatic melanoma. To determine whether this product also has potential to treat breast carcinoma, a series of in vitro and in vivo studies were made.

METHODS

Breast carcinoma cell lines and primary cultures of breast carcinoma cells were infected with DISC-GFP or DISC-human-GMCSF (DISC-hGMCSF) and the number of GFP-positive cells and GM-CSF yields were determined. In vivo efficacy of DISC-murine-GMCSF (DISC-mGMCSF) in combination with systemic chemotherapy was assessed in the murine 4T1 breast carcinoma model by direct injection into subcutaneous tumours.

RESULTS

DISC-hGMCSF was able to infect all breast carcinoma cell lines and the majority of primary breast carcinoma cultures with high efficiency, although culture-to-culture variability in infectability was noted in the latter. In the MCF-7 breast carcinoma cell line, expression of hGMCSF was found to peak over the first 24 h post-infection and drop to background levels by 7 to 14 days. In the 4T1 murine breast tumour model, injection of subcutaneous tumours led to a delay in tumour growth and, in rare cases, complete regression of visible tumour. DISC-mGMCSF and DISC-LacZ showed similar levels of efficacy. When mice were given simultaneous 5FU chemotherapy the effectiveness of DISC-mGMCSF treatment was undiminished, and up to three out of ten mice showed complete absence of visible tumour.

CONCLUSIONS

DISC-hGMCSF is able to infect human breast carcinoma cells at high efficiency and express GM-CSF. DISC-mGMCSF demonstrated efficacy in the murine 4T1 model, even during concomitant chemotherapy. Taken together these results indicate that DISC-hGMCSF may have potential for the treatment of breast carcinoma.

Cellular pharmacokinetics of carboplatin and cisplatin in relation to their cytotoxic action

We have studied the cellular pharmacokinetics of carboplatin (CBDCA), as part of the evaluation of the antitumor activity of CBDCA in cancers limited to the peritoneal cavity in comparison with cisplatin (cDDP). The uptake of CBDCA into L1210 (lymphosarcoma), CC531 (colonic carcinoma), COV413.B (human ovarian carcinoma) and NB1 (human neuroblastoma) cells was 1.5 to 13 times lower than the uptake of cDDP. The uptake of CBDCA into human ovarian carcinoma cells, taken directly from patients, was also 8-20 times lower than cDDP. Platinum concentrations, expressed as a percentage of the total intracellular Pt concentration, were similar for CBDCA and cDDP in cytosol and nucleus/membrane fractions. A second major difference between the drugs was their binding to DNA. Less CBDCA-DNA than cDDP-DNA adducts were formed after incubation at equimolar amounts of drug with isolated salmon sperm DNA (5-25 times less). A 16-69 times higher concentration of CBDCA than cDDP was needed to induce similar changes in cell growth activity (50% [3H]thymidine inhibition) in CC531 and COV413.B cells, indicating that equitoxicity can only be achieved when tumor cells are exposed to higher concentrations of CBDCA than cDDP. Similar toxicity was achieved in CC531 cells after incubation with a 16-fold higher CBDCA dose than cDDP. Comparable intracellular platinum concentrations, however, were obtained with a 10-fold higher CBDCA dose, suggesting that cellular pharmacokinetics of the drugs are different. Regarding drug uptake and pharmacokinetics the mechanism of action of CBDCA differed from cDDP at a cellular level.