Table 2.

Summary of haematological changes associated with JAK inhibitor treatment

	Platelet counts	Neutrophil counts	Lymphocyte counts	Haemoglobin levels
Abrocitinib [31, 32]	Transient ↓	No change	No change	No change
Baricitinib [33]	Transient ↑	↓	Transient ↑	Transient ↓
Filgotinib [34, 35]	↓ then stable weeks 4–24 (end of study)	↓ then stable weeks 4–24 (end of study)a	No change; no correlations with treatment groups	↑ then stable weeks 12–24 (end of study)
Peficitinib [39]	No change	Slight ↓	↓	↑
Tofacitinib [36]	NR	↓ then stabilized in LTEs	↓ then stabilized at month 48	↑ then stabilized in LTEs
Upadacitinib [41, 42]	Small transient ↓	↓ in weeks 4–8 followed by stabilization at a lower value than baseline	Small transient ↑ up to week 36	No change

A transient change is defined here as a change from baseline followed by a return to baseline levels during the period of observation.

^aA further decrease from weeks 16–24 was seen with filgotinib 100 mg twice daily, with an overall decrease to week 24 observed in patients switched from filgotinib 50–100 mg. JAK: Janus kinase; LTE: long-term extension; NR: not reported.