Background C-C Chemokine Ligand type-5 (CCR5) is overexpressed in >95% of TNBC and has been correlated with disease progression. Moreover, enhancement of DNA repair signaling by CCR5 activation may contribute to chemotherapy resistance. Therefore, blocking CCR5 may result in increased immune response against tumor cells and synergize with chemotherapy. Leronlimab (PRO 140) is a humanized monoclonal antibody to CCR5. Preclinical data showed leronlimab binds human CCR5, blocks CCR5-mediated signaling, and CCL5-induced breast cancer cell invasion. The therapeutic antibody leronlimab has been administered to over 800 healthy and HIV-1 infected individuals with good tolerance and without obvious dose-related toxicity, making it an ideal partner for chemotherapy combinations in TNBC. Methods In this ongoing phase 1B/2 study, patients with CCR5+ mTNBC with ≤2 line of therapy in the metastatic setting (no prior carboplatin) are treated with weekly subcutaneous leronlimab (3 dose levels, 3+3 dose escalation) and a fixed dose of carboplatin AUC 5 on day 1 with a 21-day dose-limiting toxicity (DLT) window, followed by expansion in 30 patients with CCR5+ mTNBC who are naïve to chemotherapy in the metastatic setting or who have failed first-line combination of chemotherapy (excluding carboplatin) and a checkpoint inhibitor in the metastatic setting. CCR5 positivity is centrally assessed by IHC and defined as >10% CCR5 staining in primary or metastatic tumor cells and/or high predominance of CCR5+ tumor-infiltrating leukocytes (TIL). Primary objectives are safety, tolerability, determination of maximum tolerated dose, and determination of the recommended phase 2 dose (RP2D). Results Fifteen patients had archived tumor tissue assessed for CCR5 expression, with 12 being CCR5 positive (median expression 20%, range 0 - 100%, and 7 out of 12 high CCR5+ TILs) . A total of ten patients (median age 51 years; median 2 prior therapies) have been enrolled at 3 dose levels (350, 525, and 700 mg). In the second cohort, 1 additional patient was inadvertently enrolled. All patients completed the DLT assessment period and no DLTs have been observed. Patients received between 3 and 27 doses of leronlimab with the number of cycles ranging from 1 to 9. Five patients remain on treatment. The most common treatment-emergent adverse events (TEAEs) by any grade were: fatigue (6/10), headache (4/10), constipation (3/10), and nausea (3/10). The following grade ≥3 TEAEs were reported: neutropenia, anemia, thrombocytopenia, hyponatremia, hypertension, diarrhea and headache. Serious Adverse Events were reported in 2 patients (grade 2 sepsis and grade 3 headache). The following leronlimab treatment related adverse events (TRAEs) occurred (all grade 1): injection site reaction in cohort 1, fatigue (n=2) and headache in cohort 2. Three carboplatin TRAEs ≥3 were reported in one patient in cohort 1: thrombocytopenia, anemia and leukopenia. Two out of seven patients eligible for response achieved a confirmed partial response, and 4 patients stable disease. Conclusions Leronlimab, in combination with carboplatin, has been well-tolerated in all 3 dose levels with early signs of anti-tumor activity in patients with CCR5+ mTNBC. The study is currently enrolling patients at the RP2D dose of leronlimab 700mg in combination with carboplatin AUC 5 in the phase 2 part of the trial. Clinical trial information: NCT03838367 Citation Format: Massimo Cristofanilli, Namita Chittoria, Sima Ehsani, Hallgeir Rui, Milana Dolezal, Lisette Stork-Sloots, Femke de Snoo, Christopher Recknor, Vandana Abramson. A phase Ib/II study of leronlimab combined with carboplatin in patients with CCR5+ metastatic triple-negative breast cancer (mTNBC) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-17-08.

In an exploratory trial treating “long COVID” with the CCR5-binding antibody leronlimab, we observed significantly increased blood cell surface CCR5 in treated symptomatic responders but not in nonresponders or placebo-treated participants. These findings suggest an unexpected mechanism of abnormal immune downmodulation in some persons that is normalized by leronlimab. Clinical Trials Registration. NCT04678830.

To theEditor—We are grateful for the opportunity to respond to these criticisms regarding our recent report. It is worth first noting that our study was a small exploratory pilot investigation, and we make no claims about treatment efficacy or mechanism but present the data to raise an interesting question about the pathogenesis of long coronavirus disease 2019 (COVID-19) syndrome. “Responders” were defined as those subjects whose symptoms consistently improved from baseline to the end of the trial. As for any clinically defined syndrome, the symptoms are necessarily interrelated. Symptom collection and scoring followed Food and Drug Administration (FDA) guidance on COVID-19 trials, with final analyses based on qualitative classifications as responder vs nonresponder, thus avoiding quantitative bias due to symptom overlap. Nonparametric testing was appropriate due to the small sample size and heterogeneity of the syndrome. While there was indeed an increase in percentage of cells expressing CCR5 from week 0 to week 8 in the overall placebo group, re-analysis of our data using rank ANCOVA (an extension of the nonparametric Wilcoxon rank-sum test to include week 0 scores as a covariate) further supports our findings: the change in the leronlimab group was significantly greater than that in the placebo group (P = .014; Figure 1A of our article). Likewise, the subgroup of leronlimab responders had CCR5% increases significantly higher than the subgroup of placebo responders (P = .006; our Figure 1B), confirming our original observation. Regardless, raw data were already provided for full transparency.

CCR5 plays a central role in infectious disease, host defense, and cancer progression, thereby making it an ideal target for therapeutic development. Notably, CCR5 is the major HIV entry co-receptor, where its surface density correlates with HIV plasma viremia. The level of CCR5 receptor occupancy (RO) achieved by a CCR5-targeting therapeutic is therefore a critical predictor of its efficacy. However, current methods to measure CCR5 RO lack sensitivity, resulting in high background and overcalculation. Here, we report on two independent, flow cytometric methods of calculating CCR5 RO using the anti-CCR5 antibody, Leronlimab. We show that both methods led to comparable CCR5 RO values, with low background on untreated CCR5+CD4+ T cells and sensitive measurements of occupancy on both blood and tissue-resident CD4+ T cells that correlated longitudinally with plasma concentrations in Leronlimab-treated macaques. Using these assays, we found that Leronlimab stabilized cell surface CCR5, leading to an increase in the levels of circulating and tissue-resident CCR5+CD4+ T cells in vivo in Leronlimab-treated macaques. Weekly Leronlimab treatment in a chronically SIV-infected macaque led to increased CCR5+CD4+ T cells levels and fully suppressed plasma viremia, both concomitant with full CCR5 RO on peripheral blood CD4+ T cells, demonstrating that CCR5+CD4+ T cells were protected from viral replication by Leronlimab binding. Finally, we extended these results to Leronlimab-treated humans and found that weekly 700 mg Leronlimab led to complete CCR5 RO on peripheral blood CD4+ T cells and a statistically significant increase in CCR5+CD4+ T cells in peripheral blood. Collectively, these results establish two RO calculation methods for longitudinal monitoring of anti-CCR5 therapeutic antibody blockade efficacy in both macaques and humans, demonstrate that CCR5+CD4+ T cell levels temporarily increase with Leronlimab treatment, and facilitate future detailed investigations into the immunological impacts of CCR5 inhibition in multiple pathophysiological processes.