Figure 3. The expression of inhibitory immune checkpoint receptors on CD8+ T-cells [38].

Extracellular vesicles

Extracellular vesicles (EVs) are membrane-bound organelles that are released from all cells to the extracellular space and biological fluids, e.g., blood. They can contain molecular cargo (e.g., RNA, protein and metabolites) and carry cell-specific markers on their surface, which unveils their cell of origin. In recent years, the focus on EVs and their role in oncogenesis, metastatic disease and resistance to cancer therapy has expanded [42]. Caivano et al . showed that many patients with haematological malignancies, including MM, had a significantly higher amount of EVs in peripheral blood (PB) compared to healthy individuals. Most EVs from the haematological patients expressed a cancer antigen specific for the individual disease on their surface. EVs from MM patients expressed CD38 [43]. The MM bone marrow microenvironment is a complex network of several different cell types, and EVs may contribute to the cross talk between malignant and non-malignant cells. Multiple studies in different types of cancer suggest that EVs may play a role in drug-resistance by several different mechanisms. For example by suppression of immune cells, by transferring drug-efflux pumps from drug-resistant cells to drug-sensitive cells, or by binding therapeutic mAbs in the circulation and thereby preventing them from reaching their target [44]. In vivo studies have revealed that lenalidomide-resistance can be transmitted from resistant to non-resistant MM cells via EVs [45]. Breast carcinoma cells, which express human epidermal growth factor receptor 2 (HER2), can be treated with trastuzumab, a mAb like DARA. These carcinoma cells secrete EVs expressing HER2, which then binds trastuzumab off target and inhibits the interaction of trastuzumab with the tumour cells [46]. The same process of capturing and neutralizing a therapeutic antibody has been observed with rituximab in lymphoma [47]. In line with the findings of HER2 expressing cells in breast cancer and CD20 expressing cells in lymphomas, an in vitro study has revealed that DARA treated MM cell lines secrete EVs expressing a CD38/daratumumab complex [48]. Likewise, EVs isolated from MM patients receiving DARA express CD38 [49]. Brennan et al. performed mass spectrometry on EVs from PB of 10 DARA treated patients (5 responding to DARA and 5 progressing on DARA) and 10 untreated healthy control EV samples. The majority of peptides identified in both the DARA treated MM EVs and healthy control EVs matched the DARA sequence. This is due to the fact that DARA is a fully human IgG. But in 9 out of 10 patients treated with DARA, they found EVs containing a peptide sequence that was not detected in the 10 control samples, with several MM patients having multiple DARA-specific peptides. This finding supports the hypothesis that DARA is present on EVs from patients treated with DARA and thus bound off target. Whether the binding of DARA off target contributes to the development of resistance is not known. In addition, the expression of the CIPs CD55 and CD59 was higher on EVs isolated from DARA treated MM patients compared to healthy controls [49]. In combination with the high amounts of CD55 and CD59 on the plasma membrane of the myeloma cells this may inhibit CDC mediated by DARA [23].

Conclusion

DARA has improved the treatment of myeloma patients significantly, but patients relapsing on DARA is still a clinical challenge. It seems that a high expression of CD38 on malignant plasma is essential for the initial response, but might be a disadvantage for the long-term response. The immune checkpoint receptor TIGIT is highly expressed on CD8+ T-cells from myeloma patients, but has not proved its importance in the clinical setting yet. Whether exhaustion of T-cells is important for the development of resistance to DARA is still not known. Furthermore, the formation of circulating EVs binding DARA off target, could potentially contribute to this development. Further research is needed.

Conflicts of interest

The author declares no conflicts of interest.

Acknowledgements

This focused review is based on the PhD thesis Resistance to daratumumab in patients with multiple myeloma [50].

References

1. Kyle, R.A. and S.V. Rajkumar, Multiple myeloma. Blood, 2008.111 (6): p. 2962-72.
2. Kumar, S.K., et al., Clinical course of patients with relapsed multiple myeloma. Mayo Clin Proc, 2004. 79 (7): p. 867-74.
3. Szabo, A.G., et al., The clinical course of multiple myeloma in the era of novel agents: a retrospective, single-center, real-world study. Clinical Hematology International, 2019. 1 (4): p. 220-228.
4. Gregersen, H., T. Silkjær, and I.B. Kristensen,Primærbehandling af myelomatosepatienter der er kandidater til højdosis kemoterapi. 2023.
5. Hansen, C.T., et al., Primær behandling af myelomatose hos patienter, som ikke er kandidater til højdosis kemoterapi med stamcellestøtte. 2022.
6. Klostergaard, A. and M. Vase, Relapsbehandling af myelomatose2022.
7. van de Donk, N., P.G. Richardson, and F. Malavasi, CD38 antibodies in multiple myeloma: back to the future. Blood, 2018.131 (1): p. 13-29.
8. de Weers, M., et al., Daratumumab, a novel therapeutic human CD38 monoclonal antibody, induces killing of multiple myeloma and other hematological tumors. J Immunol, 2011. 186 (3): p. 1840-8.
9. Overdijk, M.B., et al., Antibody-mediated phagocytosis contributes to the anti-tumor activity of the therapeutic antibody daratumumab in lymphoma and multiple myeloma. MAbs, 2015.7 (2): p. 311-21.
10. Lammerts van Bueren, J., et al., Direct in Vitro Comparison of Daratumumab with Surrogate Analogs of CD38 Antibodies MOR03087, SAR650984 and Ab79. Blood, 2014. 124 (21): p. 3474-3474.
11. Krejcik, J., et al., Daratumumab depletes CD38+ immune regulatory cells, promotes T-cell expansion, and skews T-cell repertoire in multiple myeloma. Blood, 2016. 128 (3): p. 384-94.
12. Ghose, J., et al., Daratumumab induces CD38 internalization and impairs myeloma cell adhesion. Oncoimmunology, 2018.7 (10): p. e1486948.
13. Marlein, C.R., et al., CD38-Driven Mitochondrial Trafficking Promotes Bioenergetic Plasticity in Multiple Myeloma. Cancer Res, 2019.79 (9): p. 2285-2297.
14. Lokhorst, H.M., et al., Targeting CD38 with Daratumumab Monotherapy in Multiple Myeloma. N Engl J Med, 2015. 373 (13): p. 1207-19.
15. Lonial, S., et al., Daratumumab monotherapy in patients with treatment-refractory multiple myeloma (SIRIUS): an open-label, randomised, phase 2 trial. The Lancet, 2016. 387 (10027): p. 1551-1560.
16. Usmani, S.Z., et al., Clinical efficacy of daratumumab monotherapy in patients with heavily pretreated relapsed or refractory multiple myeloma. Blood, 2016. 128 (1): p. 37-44.
17. McKeage, K., Daratumumab: First Global Approval. Drugs, 2016.76 (2): p. 275-81.
18. Kumar, S., et al., International Myeloma Working Group consensus criteria for response and minimal residual disease assessment in multiple myeloma. Lancet Oncol, 2016. 17 (8): p. e328-e346.
19. Bahlis, N.J., et al., Daratumumab plus lenalidomide and dexamethasone in relapsed/refractory multiple myeloma: extended follow-up of POLLUX, a randomized, open-label, phase 3 study. Leukemia, 2020. 34 (7): p. 1875-1884.
20. Facon, T., et al., Daratumumab, lenalidomide, and dexamethasone versus lenalidomide and dexamethasone alone in newly diagnosed multiple myeloma (MAIA): overall survival results from a randomised, open-label, phase 3 trial. Lancet Oncol, 2021.22 (11): p. 1582-1596.
21. Dimopoulos, M.A., et al., Overall Survival With Daratumumab, Lenalidomide, and Dexamethasone in Previously Treated Multiple Myeloma (POLLUX): A Randomized, Open-Label, Phase III Trial. J Clin Oncol, 2023: p. Jco2200940.
22. Szabo, A.G., et al., The real-world outcomes of multiple myeloma patients treated with daratumumab. PLoS One, 2021.16 (10): p. e0258487.
23. Nijhof, I.S., et al., CD38 expression and complement inhibitors affect response and resistance to daratumumab therapy in myeloma. Blood, 2016. 128 (7): p. 959-70.
24. Meyer, S., J.H. Leusen, and P. Boross, Regulation of complement and modulation of its activity in monoclonal antibody therapy of cancer. MAbs, 2014. 6 (5): p. 1133-44.
25. Afshar-Kharghan, V., The role of the complement system in cancer. J Clin Invest, 2017. 127 (3): p. 780-789.
26. Brandslund, I., et al., Double-decker rocket immunoelectrophoresis for direct quantitation of complement C3 split products with C3d specificities in plasma. J Immunol Methods, 1981.44 (1): p. 63-71.
27. Nijhof, I.S., et al., Upregulation of CD38 expression on multiple myeloma cells by all-trans retinoic acid improves the efficacy of daratumumab. Leukemia, 2015. 29 (10): p. 2039-49.
28. Frerichs, K.A., et al., Efficacy and safety of daratumumab combined with all-trans retinoic acid in relapsed/refractory multiple myeloma. Blood Adv, 2021. 5 (23): p. 5128-5139.
29. García-Guerrero, E., et al., Panobinostat induces CD38 upregulation and augments the antimyeloma efficacy of daratumumab.Blood, 2017. 129 (25): p. 3386-3388.
30. Szabo, A.G., et al., The Clinical Course and Life Expectancy of Patients with Multiple Myeloma Who Discontinue Their First Daratumumab-Containing Line of Therapy. Blood, 2021.138 (Supplement 1): p. 3779-3779.
31. Spencer, A., et al., Preliminary Dose-Escalation Results from a Phase 1/2 Study of GEN3014 (HexaBody®-CD38) in Patients (pts) with Relapsed or Refractory Multiple Myeloma (RRMM). Blood, 2022.140 (Supplement 1): p. 7320-7321.
32. De Goeij, B.E.C.G., et al., Hexabody-CD38, a Novel CD38 Antibody with a Hexamerization Enhancing Mutation, Demonstrates Enhanced Complement-Dependent Cytotoxicity and Shows Potent Anti-Tumor Activity in Preclinical Models of Hematological Malignancies. Blood, 2019.134 (Supplement_1): p. 3106-3106.
33. Horenstein, A.L., et al., Adenosine Generated in the Bone Marrow Niche Through a CD38-Mediated Pathway Correlates with Progression of Human Myeloma. Mol Med, 2016. 22 : p. 694-704.
34. Zelle-Rieser, C., et al., T cells in multiple myeloma display features of exhaustion and senescence at the tumor site. J Hematol Oncol, 2016. 9 (1): p. 116.
35. Ribrag, V., et al., Phase 1b trial of pembrolizumab monotherapy for relapsed/refractory multiple myeloma: KEYNOTE-013.British Journal of Haematology, 2019. 186 (3): p. e41-e44.
36. Guillerey, C., et al., TIGIT immune checkpoint blockade restores CD8 + T cell immunity against multiple myeloma. Blood, 2018.132 : p. blood-2018.
37. Frerichs, K.A., et al., Efficacy and Safety of Durvalumab Combined with Daratumumab in Daratumumab-Refractory Multiple Myeloma Patients. Cancers (Basel), 2021. 13 (10).
38. Iversen, K.F., et al., High Expression of the Costimulatory Checkpoint Factor DNAM-1 by CD4(+) T-Cells from Multiple Myeloma Patients Refractory to Daratumumab-Containing Regimens. Clin Hematol Int, 2022. 4 (3): p. 107-116.
39. Paiva, B., et al., PD-L1/PD-1 presence in the tumor microenvironment and activity of PD-1 blockade in multiple myeloma.Leukemia, 2015. 29 (10): p. 2110-3.
40. Yadav, M., et al., Tigit, CD226 and PD-L1/PD-1 Are Highly Expressed By Marrow-Infiltrating T Cells in Patients with Multiple Myeloma. Blood, 2016. 128 (22): p. 2102-2102.
41. Neri, P., et al., Immunome Single Cell Profiling Reveals T Cell Exhaustion with Upregulation of Checkpoint Inhibitors LAG3 and Tigit on Marrow Infiltrating T Lymphocytes in Daratumumab and IMiDs Resistant Patients. Blood, 2018. 132 (Supplement 1): p. 242-242.
42. Shah, R., T. Patel, and J.E. Freedman, Circulating Extracellular Vesicles in Human Disease. N Engl J Med, 2018.379 (10): p. 958-966.
43. Caivano, A., et al., High serum levels of extracellular vesicles expressing malignancy-related markers are released in patients with various types of hematological neoplastic disorders. Tumour Biol, 2015. 36 (12): p. 9739-52.
44. Namee, N.M. and L. O’Driscoll, Extracellular vesicles and anti-cancer drug resistance. Biochim Biophys Acta Rev Cancer, 2018.1870 (2): p. 123-136.
45. Yamamoto, T., et al., Understanding the Role of Extracellular Vesicles in Lenalidomide-Resistance Multiple Myeloma. Blood, 2018.132 (Supplement 1): p. 1887-1887.
46. Ciravolo, V., et al., Potential role of HER2-overexpressing exosomes in countering trastuzumab-based therapy. J Cell Physiol, 2012.227 (2): p. 658-67.
47. Aung, T., et al., Exosomal evasion of humoral immunotherapy in aggressive B-cell lymphoma modulated by ATP-binding cassette transporter A3. Proc Natl Acad Sci U S A, 2011. 108 (37): p. 15336-41.
48. Malavasi, F., et al., Molecular dynamics of targeting CD38 in multiple myeloma. Br J Haematol, 2021. 193 (3): p. 581-591.
49. Brennan, K., et al. Extracellular Vesicles Isolated from Plasma of Multiple Myeloma Patients Treated with Daratumumab Express CD38, PD-L1, and the Complement Inhibitory Proteins CD55 and CD59 . Cells, 2022. 11 , DOI: 10.3390/cells11213365.
50. Iversen, K.F., Resistance to daratumumab in patients with multiple myeloma. 2023.