Inclusion Criteria:  Able to provide written Informed Consent Aged ≥ 18 years Tumor sample obtained less than six months from the date of consent Histologically confirmed NSCLC eligible for pembrolizumab as standard of care Known tumor PD-L1 TPS score Measurable disease based on RECIST 1.1 as determined by the site Women of child-bearing potential must have a negative pregnancy test prior to trial entry and cycle 1 day 1 and should not be breast feeding. Women of child-bearing potential and men who have partners of child-bearing potential must be willing to practice highly effective contraception for the duration of the trial and for three months after the completion of treatment  Exclusion Criteria:  Less than 21 days since the last dose of intravenous anticancer chemotherapy or less than five half-lives from a small molecule targeted therapy or oral anticancer chemotherapy before the first bexmarilimab administration Any immunotherapy within preceding 3 weeks from the first bexmarilimab administration Has untreated central nervous system (CNS) metastases and/or carcinomatous meningitis identified either on the baseline brain imaging obtained during the screening period. Subjects whose brain metastases have been treated may participate provided they show radiographic stability (defined as 2 brain images, both of which are obtained after treatment to the brain metastases. These imaging scans should both be obtained at least four weeks apart and show no evidence of intracranial progression). In addition, any neurologic symptoms that developed either as a result of the brain metastases or their treatment must have returned to baseline or resolved. Any steroids administered as part of this therapy must be completed at least three days prior to study medication. Investigational therapy or major surgery within 4 weeks from the date of consent Active clinically serious infection >grade 2 NCI-CTCAE version 5.0 (Appendix 6) within preceding 2 weeks from the date of consent Subject has not recovered from the previous therapies to Grade 1 severity as classified by the NCI-CTCAE version 5.0 (except Grade 2 alopecia, neuropathy or thyroid disorders) Pregnant or lactating women The subject requires systemic corticosteroid or other immunosuppressive treatment Use of live (attenuated) vaccines for 30 days prior to the start of study treatment, d during treatment, and until last visit Has known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial. Subject is unwilling or unable to comply with treatment and trial instructions Any condition that study investigators consider an impediment to safe trial participation Prior therapy for advanced stage or metastatic disease