1. Myeloma treatment with IMiDs is associated with enhanced platelet reactivity
13th March 2019
Dr Dalia Khan

2. Introduction
Multiple myeloma (MM) associated with elevated levels of venous and arterial thromboses
Treatment with immunomodulatory drugs (IMiDs) further increases thrombosis risk
Anti-platelet agents offer more effective thromboprophylaxis in patients with IMiDs compared with other indications
Suggests platelets are of central importance in IMiD associated thrombosis
Venous and arterial thrombosis are both more prevalent in patients with myeloma, with hazard ratios of 7.5 and 1.9, respectively, compared to healthy controls. Thrombosis is correlated with reduced overall survival, and considerable morbidity including neurological compromise with stroke, post thrombotic syndrome, and pulmonary hypertension.(3–5)
The 5% pa incidence of spontaneous thrombosis in patients with myeloma is elevated to as much as 58% pa by immunomodulatory drugs (IMiDs; e.g. Lenalidomide, Pomalidomide, Thalidomide) in combination with steroids.(6) As a result, thrombo-prophylaxis with aspirin or low molecular weight heparin (LMWH) is now standard of care when IMiD therapy is initiated.
Despite this, many patients who receive thromboprophylaxis with Aspirin or LMWH experience ‘breakthrough’ VTEs. The phase 3 Myeloma XI trial reported that VTE rates were 12% with both Thalidomide and Lenalidomide therapy, despite 88% of patients receiving thromboprophylaxis. These data indicate that current anti-coagulation strategies do not effectively target the underlying cause of thrombosis in these patients.
Although LMWH offers the greatest documented reduction in IMiD-associated thrombosis risk in myeloma, the efficacy of aspirin is much greater than that seen in idiopathic VTE. (1)In keeping with this, small studies have shown increased markers of platelet activation after exposure to thalidomide. These findings suggest that improved understanding of platelet activation following IMiD exposure may help to direct the development of novel thrombo-prophylaxis strategies (including the development of IMiDs with fewer off-target effects), and this will be the focus of investigation for this project.

3. Rationale
Understanding mechanisms underlying the increased risk would allow:
Alteration of anti-platelet/anti-coagulant prophylaxis
Refinement of future drug development removing ‘off-target’ effects of IMiDs

4. Measures of platelet reactivity:
Platelet activation/degranulation/ aggregation
Courtesy:

5. CRP
TRAP-6
U46619
Modified from Rivera et al. Platelet receptors and signalling in the dynamics of thrombus formation Haematologica May 2009, 94 (5)  ; DOI:  /haematol

6. Assays- Platelet aggregation- traditional
From Chan et al. (2018) 96-well plate-based aggregometry, Platelets, DOI:  / and practical haemostasis

7. Plate based aggregometry
From Chan et al. (2018) 96-well plate-based aggregometry, Platelets, DOI:  /

8. Platelet flow cytometry-
P selectin exposure
indication of alpha granule release
Fibrinogen binding
upregulation in affinity for integrin αIIbβ3
Annexin V binding:
surrogate for Phosphatidylserine exposure
site of prothrombinase complex and activation of coagulation cascade
Courtesy : John Francis FIHR

9. Methods: Study design- Population cohorts
MGUS cohort
Smouldering Multiple Myeloma (SMM)
MM cohort: proteasome inhibitor (PI)
MM cohort: IMiD + PI + DOAC
MM cohort: IMiD + PI + ASA A
Baseline Testing: all groups B
MM cohorts on treatment
2 weeks after commencing chemotherapy C
4 weeks after commencing chemotherapy D
MM cohorts
>2 months post commencing chemotherapy

10. Results
No significant difference in baseline measures of platelet reactivity between SMM, new MM and relapsed MM *

11. IMiD treatment associated with increased Annexin binding
IMiD treated patients
Non-IMiD treated patients
p= One way matched ANOVA
p= One-way matched ANOVA
Schedule, groups, means, thinking, speculate, new imid samples etc. Conclude story, further work
Baseline
2 weeks
4 weeks
Baseline
2 weeks
4 weeks

12. IMiD Treatment increases fibrinogen binding
IMiD treated patients
ADP
IMiD treated patients CRP
CRP
P=0.04
P=0.03
Non- IMiD treated
ADP
Non- IMiD treated CRP
No difference with TRAP, numerous Epi non-responders
P=0.0006
Two way matched ANOVA: Tukey’s multiple comparison’s test

13. IMiDs enhance P-selectin exposure
IMiD treated patients CRP
IMiD treated patients ADP
IMiD treated patients ADP
P=<0.0001
P=0.0002
P=0.03
P=0.008
Non- IMiD treated patients CRP
Non- IMiD treated patients ADP
P=0.04
P=0.05
P=0.008
Two way matched ANOVA: Tukey’s multiple comparison’s test

14. Platelet aggregation not enhanced by IMiDs in vivo
IMiD treated
Non- IMiD treated

15. Donor platelet aggregation increased with in vitro addition of IMiDs- 20 minute incubation
T vs. 1UM: p=0.02
T vs. 10uM:p=0.0008
T vs. 1UM:p=0.0002
Tvs. 10uM:p<0.0001
T vs. 1UM:p=0.02
T vs. 10uM:p=0.04
Two way matched ANOVA: Tukey’s multiple comparison’s test

16. In vitro effect of dexamethasone
P=<0.0001
P=0.007
P=0.0001
P=0.003
P=0.002
P=0.03

17. Conclusion
Still early matched data for MGUS n=3, MM on IMiDs= 9, MM not on IMiDs=3, SMM n=4.
No differences in baseline measures of platelet reactivity between plasma cell dyscrasia groups
IMiDs lead to persistent increase in measures of platelet reactivity after 2 weeks of treatment
In vitro: effect of IMiDs on platelets occurs within 20 minutes : cell signalling pathways vs. transcription
Dexamethasone also leads to increase in platelet reactivity

18. Future direction Mechanistic studies:
?IMiDs acting on platelet cereblon/other ubiquitin ligases
How do IMiDs affect megakaryocyte maturation, migration and ultimate phenotype of platelets produced
Do the new CelMods have the same effect on platelet reactivity