Tri-Ad5 vaccine plus bintrafusp alfa for newly diagnosed, advanced-stage head and neck cancer not associated with human papillomavirus infection

Abstract

Background

Newly diagnosed, advanced-stage head and neck cancer (HNSCC) not associated with human papillomavirus (HPV) infection has poor survival and functional outcomes despite surgical management. Neoadjuvant immunotherapy is of interest to improve long-term outcomes.

Methods

Individuals with untreated intermediate/high risk, p16-negative (if oropharyngeal) HNSCC were eligible and underwent pre- and post-treatment tumor biopsies. Primary endpoint was pathologic complete response or clinical-to-pathological downstaging (CPD). Treatment regimen: 5 × 10¹¹ viral particles once, subcutaneously of each component of the Tri-Ad5 vaccine (ETBX-011, ETBX-061, and ETBX-051 targeting tumor-associated antigens (TAA): carcinoembryonic antigen [CEA], MUC-1, and brachyury, respectively) plus 1200 mg IV of bintrafusp alfa (anti-PD-L1 and anti-transforming growth factor-β) every 2 weeks for 2 doses. Participants returned to referring physicians for standard surgery ± adjuvant treatment if indicated.

Results

Of 6 HNSCC patients, 2 (33.3%) had CPD. There were no pathologic complete responses. 2-year recurrence free survival (RFS) was 83.3% (95% CI, 27.3%-97.5%). Adverse events were consistent with known safety profiles of each agent. There were no surgical delays.

Conclusions

In this small study, Tri-Ad5 vaccine plus bintrafusp alfa resulted in CPD in 2/6 patients. Participants also had favorable 2-year RFS compared to historical values. Ongoing tissue and peripheral immunome analyses may provide mechanistic insight. (ClincalTrials.gov Identifier: NCT04247282; IRB Approved.).

Lessons learned.

• In this small study (n = 6), Tri-Ad5 vaccine plus bintrafusp alfa given prior to surgery in newly diagnosed, advanced-stage HNSCC resulted in favorable 2-year regression-free survival, compared to historical values.

• Two of six individuals had clinical-pathological-downstaging, that is, pathological staging of surgical specimens yielded a lower American Joint Committee on Cancer (AJCC) stage compared to preoperative clinical staging.

• Ongoing correlative analyses on pre- and post-treatment tumor tissue, and peripheral blood may provide mechanistic insights.

Discussion

Outcomes following standard of care treatment for newly diagnosed, advanced stage head and neck squamous cell carcinoma (HNSCC) not associated with human papillomavirus (HPV) infection are characterized by devastating functional impairments and disease recurrence in approximately half of these individuals. For those developing recurrent/metastatic disease, the monoclonal antibody pembrolizumab targeting programmed cell death protein 1 (PD-1) improves survival outcomes as monotherapy (combined positive score ≥ 1) or in combination with chemotherapy. However, relapsed disease remains incurable. The 4-6 week planning period prior to definitive surgery presents a window of opportunity for neoadjuvant immunotherapy aimed at improving recurrence free survival (RFS). Several small clinical studies suggest that perioperative immune checkpoint blockade (ICB) may reduce rates of disease relapse, and a phase III trial of neoadjuvant plus adjuvant pembrolizumab is currently underway in resectable, locally advanced HNSCC (KEYNOTE-689 [NCT03765918]). Here we report results from a small pilot combination neoadjuvant immunotherapy regimen.

From February 2021 to May 2021, we enrolled individuals with previously untreated intermediate/high-risk, p16-negative (if oropharyngeal) HNSCC (n = 6). Trial schema is depicted in Figure 1. Trial participants underwent pre- and post-treatment tumor biopsies. Participants received bintrafusp alfa (BA), a bifunctional fusion protein (anti-PD-L1 monoclonal antibody fused to the TGF-β-RII receptor extracellular domain) and the recombinant Tri-Ad5 vaccine, consisting of ETBX-011, ETBX-061, and ETBX-051 targeting three tumor-associated antigens carcinoembryonic antigen, MUC-1, and brachyury, respectively. At treatment initiation, trial participants received one dose of 5 × 10¹¹ viral particles of each ETBX-011, ETBX-061, and ETBX-051 plus BA 1200 mg IV (followed by an additional dose of BA 1200 mg IV 2 weeks later). Trial participants then returned to their referring provider for standard-of-care surgery followed by adjuvant radiotherapy ± chemotherapy if indicated.

Figure 1.

Trial Schema. Following enrollment, participants underwent pre-treatment biopsy, treatment with bintrafusp alfa + Tri-Ad-5 vaccine, and then post-treatment biopsy. Participants then returned to the community for standard-of-care surgery and adjuvant treatment (if indicated).

Patient demographics are listed in Table 1. Adverse events were graded according to the National Cancer Institute Common Toxicity Criteria for Adverse Events Version 5.0 and treatment-related adverse events (TRAEs) are listed in Table 2.

Table 1.

Patient characteristics prior to, during, and after trial enrollment.

Age at enrollment (years)
Median (range)	63.5 (31-81)
Sex, N (%)
Male	1 (16.6)
Female	5 (83.4)
Ethnicity, N (%)
Black	1 (16.6)
Hispanic	1 (16.6)
White	4 (66.7)
Smoking history, N (%)
Yes	3 (50)
No	3 (50)
Tumor site, N (%)
Larynx	1 (16.6)
Oral cavity	5 (83.4)
Clinical T classification, N (%)
T2	4 (66.7)
T3	0
T4	2 (33.3)
Clinical N classification, N (%)
N0-N1	2 (33.3)
N2	4 (66.7)
N3	0
AJCC (8th edition) stage at study entry, N (%)
II	2 (33.3)
III	0
IV	4 (66.7)
Days from first neoadjuvant treatment to surgery
Median (range)	23.5 (20-82)
Pathologic stage determined from surgical specimen, N (%)
I	0
II	2 (33.3)
III	1 (16.6)
IV	3 (50)
Free tissue transfer reconstruction
Yes	4 (66.7)
No	2 (33.3)
Number of doses of bintrafusp alfa
1	1 (16.6)
2	5 (86)
Adjuvant treatment
None	2 (16.6)
Radiotherapy	3 (50)
Chemotherapy and radiotherapy	0

Table 2.

Treatment-related adverse events (TRAEs).

Event	Grade
	1	2	3	4
	N (%)	N (%)	N (%)	N (%)
Anemia	1(16.7)
Epistaxis	3(50
Fatigue	3(50)
Flu-like symptoms	2(33.3)
Hypothyroidism		1(16.7)
Infusion-related reaction		1(16.7)
Injection site reaction	3(33.3)	2(33.3)
Keratoacanthoma	1(16.7)
Neck edema	1(16.7)
Oral hemorrhage	2(33.3)
Oral pain		1(16.7)
Pneumonitis				1(16.7)
Rash	1(16.7)
Tumor hemorrhage	1(16.7)

TRAEs graded by CTCAEv5.0. There were no grade 5 TRAEs.

No trial participants experienced a delay in planned surgery. One individual expired in the post-operative period due to an ST elevation myocardial infarction. Autopsy revealed extensive peripheral arterial disease undiagnosed at the time of trial enrollment.

Per American Joint Committee on Cancer (AJCC) staging, 2/6 trial participants staged as clinical stage IVA at enrollment experienced clinical-to-pathologic downstaging (CPD). CPD refers to a situation where pathological staging (post-operative, resected tissue-based staging) is a lower AJCC stage than clinical staging (based on clinical exam and imaging). There were no pathologic complete responses or radiographic responses by RECISTv1.1. One- and two-year RFS and one- and two-year overall survival (OS) were each 83.3% (95% CI, 27.3%-97.5%). Correlative analyses from pre- and post-treatment tumor samples and peripheral blood aimed at examining pharmacodynamic immune parameters are ongoing.

Trial Information

Disease	Previously untreated intermediate/high risk, non-HPV associated, squamous cell carcinoma of the head and neck
Stage of disease/treatment	T1-T4, N0-N3, M0 stage II, III, or IV
Prior therapy	None
Type of study	Phase ½
Primary endpoint	Pathologic complete response or clinical-to-pathological downstaging
Secondary endpoints	- Estimate the rate of grade 3 or 4 immune-related adverse events (irAEs) - Determine the rate of treatment-related adverse events (AE) causing a delay of 4 weeks or more beyond planned surgery - Estimate the response rate of the primary disease by CT imaging (RECIST) - Estimate the one- and two-year recurrence-free survival - One- and two-year overall survival

Drug Information

Generic/working name	Bintrafusp alfa
Company name	EMD Serono
Drug Class	Anti-PD-L1 and anti-transforming growth factor-β
Dose	1200
Unit	Mg
Route	Intravenously
Schedule of administration	Every 2 weeks

Drug Information

Generic/working name	Tri-Ad5 vaccine, comprised of ETBX-011, ETBX-061, and ETBX-051
Company name	ImmunityBio
Drug class	Therapeutic vaccine
Dose	5 × 1011
Unit	Viral particles
Route	subcutaneously
Schedule of administration	Once

Patient Characteristics: See Table 1

Assessment, Analysis, and Discussion

Completion	Study completed
Investigator’s Assessment	Active but results overtaken by other developments

Despite maximal treatment, often consisting of surgery with adjuvant radiotherapy with or without chemotherapy, poor outcomes are observed in patients with head and neck squamous cell carcinoma (HNSCC) not associated with human papilloma virus infection (HPV).¹ Locoregional recurrence or distant metastasis will develop in 35% of patients with non-HPV-associated HNSCC in the first year and five-year overall survival (OS) is less than 50%.² Additionally, standard-of-care treatments for advanced-stage HNSCC leave cured patients with devastating functional impairments.³ More efficacious and less toxic treatments are needed for advanced-stage, non-HPV-associated, HNSCC.

Neoadjuvant immunotherapy during the treatment planning window prior to definitive surgery (as opposed to post-surgery adjuvant treatment) may allow enhanced systemic anti-tumor immunity and improve recurrence-free survival (RFS) through egress of tissue resident tumor antigen-specific T cells, from the tumor microenvironment into circulation, that otherwise would have been removed with definitive surgical treatment.^4,5 Systemic neoadjuvant treatment is currently not the standard of care for resectable HNSCC, but multiple phase II clinical studies have demonstrated improved RFS (when compared to historical values) with immune checkpoint blockade (ICB) prior to definitive surgical management of HNSCC.^6-10 KEYNOTE-689¹¹ is a pivotal, randomized phase III clinical trial powered to determine if neoadjuvant and adjuvant pembrolizumab (anti-PD-1) improves RFS for locally advanced resectable HNSCC (NCT03765918).

Combination neoadjuvant immunotherapies that enhance anti-tumor immunity through mechanisms distinct from blockade of PD-1/PD-L1 may further enhance pathologic responses and RFS improvements derived from therapeutic PD-1/PD-L1 blockade. We previously reported favorable pathologic response and RFS data from NCT04247282 (Arm A), utilizing BA (a bifunctional fusion product combining anti-PD-L1 and sequestration of TGF-β) in individuals with resectable HPV-negative HNSCC.⁹ Correlative analyses demonstrated an increase in circulating tumor-specific CD8+ T cells following BA treatment; an observation associated with decreased expression of the tissue retention marker CD103 on tissue-resident tumor-specific TIL after treatment compared to with BA.⁵ More work is needed to determine whether increased efflux of tumor-specific T cells from the tumor into circulation is causally associated with improved RFS.

Here were reported clinical results from Arm B of NCT04247282, which added a vaccine targeting the TAAs CEA, MUC1, and brachyury (TriAd-5) to BA. As in the study of BA monotherapy,⁹ we observed RFS favorable to historical figures: 2-year RFS = 83.3% (95% CI, 27.3%-97.5%). 2/6 patients experienced clinical-to-pathologic downstaging, suggesting that this regimen is active in some individuals’ tumors.

This study closed early following the announcement of negative preliminary analyses from phase III studies using BA in other malignancies and other administrative factors. The resulting small sample size is a limitation. Additionally, BA will not be developed further. Nonetheless, results from this study including BA are relevant since interest in the addition of TGF-β blockade to ICB remains active given the promising mechanisms of enhanced egress of tissue-resident tumor-specific TIL in correlative studies.

Finally, in the neoadjuvant, potentially curative setting, the side effect profile of treatments is an important consideration. After TriAd5 vaccine administration in this study, patients experienced mild, transient flu-like illness as observed in the phase 1 TriAd5 monotherapy trial.¹² Given the potential for the more severe side effects with ICB such risks will need to be weighed against potential clinical benefit as more is learned about ICB in this clinical setting.

Funding

This study was funded by the Intramural Program of the Center for Cancer Research, National Cancer Institute, NIH (ZIA BC 010666) with this research being part of individual Cooperative Research and Development Agreements (CRADAs) between the National Cancer Institute and the following individual entities:

(1)EMD Serono Research & Development Institute, Inc., Billerica, MA, USA, an affiliate of Merck KGaA (CrossRef Funder ID: 10.13039/100004755)

*2)ImmunityBio.

Conflicts of interest

Patrick Soon-Shiong: OI, IP for ImmunityBio.

Data availability

Raw data will be provided upon reasonable request.