Phase 1/2 study of pepinemab, an inhibitor of semaphorin 4D, in combination with pembrolizumab as first-line treatment of recurrent or metastatic head and neck cancer (KEYNOTE-B84)

e18033

Background: Immunosuppressive myeloid cells in the tumor microenvironment (TME) limit the efficacy of immune checkpoint inhibitors (ICIs) in head and neck squamous cell carcinoma (HNSCC). Preclinical and clinical studies demonstrated that antibody blockade of semaphorin 4D (SEMA4D) promotes tumor infiltration and activation of DCs and CD8+ T cells and reverses immunosuppression, including attenuation of MDSC recruitment and function, leading to enhanced efficacy of ICIs. Pepinemab, a SEMA4D blocking antibody, in combination (combo) with avelumab provided clinical benefit in some patients with ICI-resistant and PD-L1-low NSCLC. Pembrolizumab (pembro) is approved as monotherapy or in combo with chemo for the first-line treatment of recurrent or metastatic (R/M) HNSCC, representative of a class of tumors that express higher levels of SEMA4D and MDSC. The primary hypothesis of this proof-of-concept study is that pepinemab in combo with pembro will yield increased clinical benefit compared to the reported activity for pembro monotherapy in R/M HNSCC. Methods: KEYNOTE-B84 (NCT04815720) is a single-arm open-label study evaluating the safety, efficacy, and PK/PD of pepinemab in combo with pembro as first-line treatment of R/M HNSCC. Subjects with measurable disease per RECIST1.1, ECOG 0 or 1, are eligible; subjects who have received prior ICIs or other systemic treatment for R/M HNSCC are excluded. The study includes a safety run-in (n = 3) and dose-expansion phase (maximum n = 62). Pepinemab, previously found to be well-tolerated in combo with other ICIs, will be evaluated initially at the highest intended dose of 20 mg/kg, in combo with 200 mg pembro, both administered i.v. Q3W. The dose expansion phase plans to include nearly equal distribution of subjects who have tumor PD-L1 combined positive scores (CPS) of < 20 and ≥20. The primary efficacy endpoint is ORR, and the secondary endpoints are PFS, DoR, and OS, as well as exploratory biomarker analyses. Pre- and on-treatment biopsies will be collected for evaluation of immune contexture in TME. Results: The safety run-in phase (n = 3) is complete, and the combo appeared to be well-tolerated with no DLTs observed; SMC approved continuation to dose expansion. Strikingly, two of the three patients have been observed to experience a complete response (CR). Biomarker analysis revealed that tumors in both responders expressed low levels of PD-L1 (CPS < 20). The third patient progressed prior to first scan, suffering several unrelated SAEs attributed to a pre-existing co-morbidity. Conclusions: The ongoing KEYNOTE-B84 study completed the initial safety run-in phase, with two of three subjects achieving CR. Phase 2 will evaluate pepinemab, a SEMA4D inhibitor, as a novel strategy to potentially overcome resistance and enhance activity of pembro in R/M HNSCC. Clinical trial information: NCT04815720.

A Phase Ib/II Study of Pepinemab in Combination with Avelumab in Advanced Non-Small Cell Lung Cancer

PURPOSE

The CLASSICAL-Lung clinical trial tested the combination of pepinemab, an IgG4 humanized mAb targeting semaphorin 4D, with the PD-L1 inhibitor avelumab to assess the effects of coupling increased T-cell infiltration and reversal of immune suppression via pepinemab with sustained T-cell activation via checkpoint inhibition.

PATIENTS AND METHODS

This phase Ib/II, single-arm study was designed to evaluate the safety, tolerability, and efficacy of pepinemab in combination with avelumab in 62 patients with advanced non-small cell lung cancer (NSCLC), including immunotherapy-naïve (ION) patients and patients whose tumors progressed following anti-PD-1/L1 monotherapy (IOF). The main objectives were to evaluate safety/tolerability, establish a recommended phase 2 dose (RP2D), obtain a preliminary evaluation of antitumor activity, and investigate candidate biomarker activity.

RESULTS

The combination was well tolerated with no major safety signals identified. Pepinemab, 10 mg/kg with avelumab, 10 mg/kg, every 2 weeks, was selected as the RP2D. Among 21 evaluable ION patients, 5 patients experienced partial responses (PR), 4 patients evidenced clinical benefit ≥1 year, and the disease control rate (DCR) was 81%. Notably, overall response rate with the combination therapy was higher than previously reported for single-agent avelumab in the PD-L1-negative/low population. Among 29 evaluable IOF patients, the combination resulted in a DCR of 59%, including 2 PR and 7 patients with durable clinical benefit of ≥23 weeks. Biomarker analysis of biopsies demonstrated increased CD8 T-cell density correlating with RECIST response criteria.

CONCLUSIONS

The combination of pepinemab with avelumab was well tolerated in NSCLC and showed signs of antitumor activity in immunotherapy-resistant and PD-L1-negative/low tumors.

Integrated biomarker study of neoadjuvant pepinemab and nivolumab in patients with resectable metastatic melanoma

10061

Background: SEMA4D has broad immunomodulatory effects in the tumor microenvironment (TME); blocking SEMA4D in combination with checkpoint inhibitors (CI) promotes immune infiltration, reduces recruitment of myeloid cells, enhances T cell activity, and promotes tumor regression. We hypothesized that adding pepinemab (VX15/2503), which targets SEMA4D, to CI would increase immunomodulatory effects and augment response in melanoma (NCT03769155). Methods: Patients with resectable stage IIIB/C/D melanoma were enrolled to control (no neoadjuvant therapy) or treatment cohorts (n = 8 in four cohorts of pepinemab plus nivolumab, ipilimumab, nivolumab/ipilimumab or alone). Here we report results from patients receiving two doses of nivolumab (360mg) and pepinemab (15mg/kg) every three weeks followed by surgery. Primary endpoint was T cell infiltration into the TME; secondary endpoints include pathologic response rates, peripheral immune profile, and safety. Results: Ten patients are reported: two were controls, eight received neoadjuvant therapy. Two patients had pathologic complete response, one had a near-complete pathologic response ( < 1% viable tumor), one had a partial response (41% viable tumor) and four had stable disease (73-90% viable tumor). All neoadjuvant patients underwent surgery without delay; one patient experienced grade 3 post-operative cellulitis. There were two treatment-related grade 3 adverse events (weakness and arthralgia). Pharmacodynamic studies confirmed saturation of PD-1 and SEMA4D in peripheral and tumor-infiltrating T cells. T/B cell (CD8+/CD20+) ratios, a surrogate for T cell infiltration, were higher in post-treatment tumors compared to pre-treatment and were higher in the tumor bed compared to normal adjacent tissue. Flow cytometric evaluation identified an increase in CD26hi CD4+ and CD8+ tumor-infiltrating effectors in treated patients compared to controls and an increase in peripheral frequencies of the PD-1-responsive effector HLA-DR+CD38+Ki67+ CD4+ and CD8+ T cells following treatment. Treatment increased infiltration of myeloid populations into the TME, increased expression of PD-L1 on TME myeloid populations, and increased expression of the SEMA4D receptor Plexin-B2 on the surface of TME CD45− and M2 macrophages and MDSC. Conclusions: Neoadjuvant nivolumab and pepinemab results in increased T cell infiltration with excellent major response rate (38%) and expected safety profile. We continue to enroll patients using other rational combinations of pepinemab and CI. Clinical trial information: NCT03769155.

Interim subgroup analysis for response by PD-L1 status of CLASSICAL-Lung, a phase Ib/II study of pepinemab (VX15/2503) in combination with avelumab in advanced NSCLC

3011

Background: Antibody blockade of semaphorin 4D (SEMA4D, CD100) promotes tumoral dendritic cell and CD8+ T cell infiltration and reduces function and recruitment of immunosuppressive myeloid cells. Importantly, these mechanisms to overcome immune exclusion and suppression have been shown to complement immune checkpoint therapies in preclinical models. Pepinemab is an IgG4 humanized monoclonal antibody targeting semaphorin 4D. The CLASSICAL-Lung clinical trial tests the combination of pepinemab with avelumab to couple T cell activation via checkpoint inhibition with beneficial modifications of the immune microenvironment via pepinemab. Methods: This phase 1b/2, single arm, first-in-human study is designed to evaluate the safety, tolerability and efficacy of pepinemab with avelumab in 62 patients (pts) with advanced (stage IIIB/IV) non-small cell lung cancer (NSCLC), including immunotherapy-naïve (ION) pts and pts whose tumors progressed following immunotherapy (IOF). Results: Among 21 evaluable ION pts, 5 experienced partial response (PR), 3 pts had clinical benefit ≥ 1 year, and the disease control rate (DCR) is 81%. Pts enrolled in this study were observed to have lower PD-L1 expression relative to prior single agent studies (likely due to approval of pembrolizumab for first line therapy). We, therefore, performed subgroup analysis for response by PD-L1 status. The objective tumor response (ORR) in the PD-L1 negative and low population ( < 80% TPS by Dako 73-10 assay) appears to be approximately 2-2.5 fold greater with combination therapy than with historical single agent immune checkpoint controls. Notably, 97% of pts who experienced PR or SD were reported to have tumors with negative or low PD-L1 expression. Among 29 evaluable IOF pts, the combination resulted in 59% DCR, including 2 PR and 7 patients with durable clinical benefit of ≥ 23 weeks. Biomarker analysis of pre- and on-treatment biopsies confirmed increased CD8+ T cell density correlating with response. Surprisingly, analysis of myeloid-derived suppressor cells (MDSCs) revealed a relative paucity of these cells in pretreatment NSCLC biopsies as compared to other cancer indications such as HNSCC. Conclusions: This trial is nearing completion with only 5 of 62 subjects remaining on study. Preliminary data suggest the combination is well tolerated and shows signs of increased antitumor activity, particularly in PD-L1 negative or low tumors. Updated clinical response data and immunophenotypic analyses will be presented. Clinical trial information: NCT03268057 .

Antibody blockade of semaphorin 4D to sensitize pancreatic cancer to immune checkpoint blockade

26

Background: Pancreatic ductal adenocarcinoma (PDAC) carries a dismal prognosis, and will soon become the second leading cause of cancer mortality. Unfortunately, T-cell directed immunotherapies have failed to demonstrate efficacy in PDAC. These failures may in part be mediated by an immunosuppressive tumor microenvironment (TME). Semaphorin 4D (Sema4D) is a glycoprotein which binds its cognate receptors Plexin B1/B2. Here we present our work in blocking Sema4D in a murine model of PDAC. Methods: C57b/6 mice were orthotopically injected with PDAC line (KP2) derived from KRASG12D,TP53Flox/Wt;P48-Cre autochthonous tumors and confirmed for disease by ultrasound. Mice were treated with FOLFIRINOX (5-FU, Irinotecan, Oxaliplatin, weekly), immune checkpoint blockade (ICB) (anti-PD1, anti-CTLA-4 mAbs bi-weekly), and anti-Sema4D mAB (bi-weekly). Human and mouse circulating and tumor infiltrating leukocytes were interrogated through flow cytometry (FACS) for immune subset and expression of Sema4D and Plexin receptors. Archived human PDAC tissues were assessed through quantitative immunohistochemistry (IHC) for presence of Sema4D positive infiltrate. Results: Both FACS and IHC analysis of human PDAC specimens confirm the presence and increased prevalence over normal pancreata of Sema4D lymphocytes and Plexin B1/B2 expressing tumor associated macrophages (TAMs). KP2 orthotopically injected mice exhibited longer survival when treated with the triple combination of FOLFIRINOX, ICB, and anti-Sema4D antibody, compared to FOLFIRINOX alone, FOLFIRINOX plus ICB, or FOLFIRINOX plus anti-Sema4D antibody (P < 0.02). Flow cytometric analysis of anti-Sema4D and ICB treated murine tumors show a doubling of penetration by CD 8+ effector T cells within tumors compared to control groups (P = 0.03). A loss in Sema4D fluorescence signal via FACS in tumor-infiltrating CD3+ leukocytes was observed in mice treated with anti-SEMA4D, confirming penetration and target blockade within the TME. Conclusions: Sema4D and Plexin B1/B2 leukocytes penetrate human PDAC tumors, and treatment with Sema4D blocking antibody improved response to ICB in combination with standard of care FOLFIRINOX in preclinical murine studies.

Interim results from a phase Ib/II study of pepinemab in combination with avelumab in advanced NSCLC patients following progression on prior systemic and/or anti-PDx therapies

75

Background: Despite progress of immune checkpoint therapies, many cases of non-small cell lung cancer (NSCLC) are refractory or acquire resistance to current therapies. Antibody blockade of semaphorin 4D (SEMA4D, CD100) can overcome resistance mechanisms of immune exclusion and myeloid suppression. Importantly, combinations of anti-SEMA4D with various immunotherapies enhanced T cell infiltration and activity, as well as durable tumor regression in preclinical models. Pepinemab (VX15/2503) is a first-in-class humanized monoclonal antibody targeting SEMA4D. Methods: The CLASSICAL-Lung clinical trial (NCT03268057) evaluates the combination of pepinemab with anti-PD-L1 antibody avelumab to couple beneficial modifications of the immune microenvironment via pepinemab with immune activation via checkpoint inhibition. This ongoing study evaluates the safety, tolerability and efficacy of the combination in patients with advanced (stage IIIB/IV) NSCLC, including immunotherapy-naïve (ION) patients and patients whose tumors progressed during or following immunotherapy (IOF). Results: The combination was well tolerated with no major safety signals identified. Among 29 evaluable IOF patients, two experienced confirmed partial response (PR) with 63% and 52% tumor reduction on study following acquired resistance to prior treatment with pembrolizumab, 15 additional patients experienced stable disease, and at least 5 patients with durable clinical benefit of ≥ 23 weeks. Among 21 evaluable ION patients, 5 experienced PR, clinical benefit ≥ 1 year was observed in 3 patients, and Disease Control Rate was 81%. Analysis of pre- and on-treatment biopsies demonstrated increased CD8+ T cell density correlating with response, reduction or elimination of tumor in 11/13 biopsies from subjects with PR or SD. Conclusions: Interim analysis suggests the combination of pepinemab plus avelumab is well tolerated and shows initial clinical signals of antitumor activity. Updated clinical response data (minimum of 6 mo. follow-up), as well as additional immunophenotyping of both inflammatory and suppressive myeloid cells will be presented. Clinical trial information: NCT03268057.

Preliminary results from CLASSICAL-Lung, a phase 1b/2 study of pepinemab (VX15/2503) in combination with avelumab in advanced NSCLC

2601

Background: Rational combination therapies are needed to overcome resistance mechanisms in NSCLC. Pepinemab is an IgG4 humanized monoclonal antibody targeting semaphorin 4D (SEMA4D, CD100). In vivo preclinical models demonstrated antibody blockade of SEMA4D promoted immune infiltration and reduced function and recruitment of immunosuppressive myeloid cells within the tumor. Importantly, preclinical combinations of anti-SEMA4D with various immunotherapies enhanced T cell activity and tumor regression. The CLASSICAL-Lung clinical trial tests the combination of pepinemab with avelumab to couple immune activation via checkpoint inhibition with beneficial modifications of the immune microenvironment via pepinemab. Methods: This ongoing phase 1b/2, open label, single arm, first-in-human combination study is designed to evaluate the safety, tolerability and efficacy of pepinemab in combination with avelumab in 62 patients (pts) with advanced (stage IIIB/IV) NSCLC (NCT03268057). The trial is split into dose escalation (n = 12) and dose expansion (n = 50) phases and includes 2 cohorts; 1) pts who are immunotherapy naïve, and 2) pts whose tumors progressed during or following immunotherapy (IO failure). Pts in the dose escalation cohorts received ascending doses of pepinemab i.v. (5, 10, 20 mg/kg, Q2W) in combination with avelumab i.v. (10mg/kg, Q2W). Results: Dose escalation is complete and the RP2D was selected as 10mg/kg pepinemab, Q2W. No pts experienced a TRAE leading to study discontinuation or death. The most frequent related AEs were grades 1 or 2 fatigue, pyrexia, or chills; no grade 3 AEs occurred in more than one subject. One DLT, a grade 3 pulmonary embolism occurred in the 10mg/kg pepinemab cohort, and resolved without reoccurrence. The disease control rate for pts treated > 2 months is 90% (19/21), and, at this early stage, a PR with a 49% reduction in target lesion was observed in at least 1 of 8 pts in the IO failure cohort. Updated data from the dose expansion phase will be presented. Conclusions: Preliminary data suggest the combination is well tolerated and shows initial signals of antitumor activity. Dose escalation is complete and the expansion phase is ongoing. Clinical trial information: NCT03268057.