A phase Ia dose-escalation trial of Ametumumab (a fully human monoclonal antibody against epidermal growth factor receptor) in patients with advanced solid malignancies

Abstract

Background:

Epidermal growth factor receptor (EGFR) is a well-known target for cancer treatment. However, the authorized anti-EGFR monoclonal antibodies generally cause several toxic effects, especially severe cutaneous toxicities as well as infusion reactions, and the clinical indications are limited. Here we developed Ametumumab, a fully human recombinant anti-EGFR monoclonal antibody.

Objectives:

To assess the safety, tolerability, pharmacokinetics (PK), and immunogenicity of Ametumumab.

Design:

A first-in-human phase Ia dose escalation study of Ametumumab in patients with advanced solid malignancies.

Methods:

An open-label, first-in-human dose escalation study was done in 22 patients with advanced malignancies who received six ascending dosages ranging from 75 to 750 mg/m². Following a single dosage and a 28-day dose-limiting toxicity (DLT) monitoring period, patients were given repeated doses weekly. Blood samples were taken to determine the PK parameters of Ametumumab and anti-drug antibody concentrations. Every 8 weeks, radiographic tumor evaluations were conducted.

Results:

In this trial, no DLT was observed, and the maximum tolerated dose was not reached at doses up to 750 mg/m². There were no severe adverse events but mild and moderate adverse effects, such as headache, proteinuria, and rash. Single-dose PK results demonstrated a straightforward linear relationship with dosage escalation. The medication concentrations accumulated and attained steady-state after four rounds of injections. It was calculated that 10 patients with disease control would be observed in the 22 evaluable patients. The disease control rate was 45.5%.

Conclusion:

The Ametumumab was well tolerated and safe in patients with advanced solid malignancies, exhibiting minimal immunogenicity, a long half-life, high levels of drug exposure in the blood, and preliminary effectiveness.

Registration:

The trial was registered with CTR20170343 on 10 April 2017, The China Center for Drug Evaluation.

Introduction

Due to its widespread expression and a vital role in tumor treatment, the epidermal growth factor receptor (EGFR), also known as HER1 or ErbB1, has become an essential and traditional target for cancer therapy.^1–3 The activation of EGFR pathway occurs by ligand binding and receptor dimerization, which then activates downstream signaling pathways such as RAS/Raf/MAPK and PI-3K/Akt. The stimulations indicated above may affect cell growth, proliferation, differentiation, metastasis, healing of damage, and apoptosis inhibition.^4,5 In addition, EGFR is overexpressed in a wide variety of human epithelial cancers.^6,7 Both EGFR expression and overexpression have been linked to early disease development, poor survival, and resistance to treatment.^4,8

To date, four monoclonal antibodies directed against the EGFR have been approved: cetuximab, panitumumab, nimotuzumab, and necitumumab. Panitumumab and necitumumab are both fully human monoclonal antibodies. However, hypomagnesemia, grade 3–4 skin toxicity, and gastrointestinal toxicity are more common in individuals treated with panitumumab than in those treated with cetuximab.^9,10 Necitumumab’s effectiveness in the treatment of metastatic non-small-cell squamous lung cancer brings little benefits to patients.¹¹ Although nimotuzumab is a highly humanized monoclonal antibody that has been approved in China, its indications are limited (suited for stage III/IV nasopharyngeal cancer with positive EGFR expression in combination with radiotherapy).¹² Cetuximab has been authorized as a first-line therapy option for patients with advanced colorectal cancer, as well as head and neck squamous cell carcinoma.^13–15 However, it is a chimeric monoclonal antibody with a high immunogenicity, a significant risk of hypersensitivity, and a high incidence of cutaneous and gastrointestinal damage.¹⁵ As a result, the authorized EGFR monoclonal antibodies all have certain shortcomings, and it is necessary to develop a new novel fully human anti-EGFR monoclonal antibody drug with improved safety and effectiveness.

As a recombinant fully human monoclonal antibody directed against EGFR, Ametumumab was generated by affinity maturation of a large phage display human antibody library. Ametumumab is an IgG1 subtype antibody with a novel sequence and an epitope that somewhat overlaps but is distinct from cetuximab. Our preclinical investigations demonstrated that Ametumumab had a considerably longer half-life in rats and cynomolgus monkeys than cetuximab. After animal in vivo administration, Ametumumab was found to accumulate into the tumor area and showed fewer target-related adverse events (AEs), as well as no evident damage to the skin, respiratory, cardiovascular, or neurological systems. Ametumumab’s antitumor activity in nude mice was comparable to that of cetuximab.

The purpose of this research was to determine the tolerability, safety, and pharmacokinetic (PK) properties of Ametumumab in individuals with advanced malignant solid tumors after single-dose and multiple-dose administrations. In addition, the recommended phase II dosage (RP2D) was calculated in this study, since potentially successful indications were tested.

Methods

Design

We performed a phase Ia escalation study of Ametumumab on an open-label, non-randomized, single-arm basis (CTR20170343). The main endpoint was utilized to assess the safety and PK of Ametumumab, as well as to identify the dose-limiting toxicity (DLT), maximum tolerated dose (MTD), and RP2D. The secondary endpoint was used to assess Ametumumab’s antitumor activity and immunogenicity in humans and investigate the relationship between genetic mutation status (KRAS, NRAS, and BRAF) and effectiveness.

The initial dose level of Ametumumab was determined to be 75 mg/m² based on preclinical data. According to the modified Fibonacci design scheme, the dosage amplitude was raised by 100%, 100%, 50%, 33%, and 25%, respectively. Six dosage cohorts of 75, 150, 300, 450, 600, and 750 mg/m², respectively, were designed. During the single-dose phase (within 28 days of the DLT observation period after the first dosage), cohorts of 3–6 patients were sequentially recruited in the dose range of 75–750 mg/m² to complete the observation of DLT at different dose levels. Following the DLT observation period, individuals may join the multiple-dose phase and receive Ametumumab in continued weekly doses for 6 weeks if the medicine was well tolerated. Following the multiple-dose period, the therapy was maintained until the disease progression or intolerable toxicity occurred (continued administration phase).

DLT was defined as the incidence of any of the following conditions within the first 28 days of single-dose therapy, as graded by the National Cancer Institute’s Common Terminology Criteria for Adverse Events (NCI-CTCAE) V4.03¹⁶: non-hematological toxicity of grade 3 or 4 (save for rash); hematological toxicity of ⩾grade 3, including but not limited to grade 4 neutropenia lasting ⩾7 days, and febrile neutropenia. Rashes that met the following criteria were also defined as DLT: grade 4 rash, three instances of grade 3 rash, and three consecutive infusion pauses due to grade 3 rash.

MTD was determined as follows: if DLT occurred in two or more patients treated at the same dosage level throughout the 28-day observation period, dose escalation would be stopped, and the dose level below would be designated the MTD.

Inclusion and exclusion criteria

Patients with histologically or cytologically verified diagnosis of advanced solid cancer for whom earlier therapies had failed (i.e. patients who had no response to treatment or tolerated conventional therapy) or for whom no standard treatment regimen available were eligible. Patients should be between the ages of 18 and 70, and have at least one measurable lesion according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1,¹⁷ Eastern Cooperative Oncology Group performance of 0 to 1, life expectancy ⩾12 weeks, hemoglobin ⩾90 g/L, absolute granulocyte count ⩾1.5 × 109/L, platelet count ⩾75 × 109/L, total bilirubin ⩽1.5 × upper limit of normal (ULN), aspartate aminotransferase and alanine aminotransferase ⩽2.5 × ULN, and serum creatinine ⩽1.5 × ULN.

Known symptomatic central nervous system or brain metastases; symptomatic autoimmune illness; known allergy to protein preparations, monoclonal antibodies, or components or excipients of any research medicine; and unexplained fever >38.5°C were all exclusion criteria.

Safety

Throughout the trial, safety was monitored by tracking AEs, physical examinations, changes in vital signs, and clinical test data. The Medical Dictionary for Regulatory Activities was used to code AEs, and the NCI-CTCAE V4.03 was used to evaluate AEs and laboratory results.

Pharmacokinetics

Blood samples for Ametumumab serum concentration analysis were obtained within 0.5 h before Ametumumab infusion (−0.5 h) and then at 1.0, 2.0, 2.5, 4, 8, 24, 48, 96, 168, 240, 336, 504, and 672 h following the commencement of infusion in the single-dose phase. In the multiple-dose phase, blood samples were collected within 0.5 h before the first and sixth infusions, as well as at 1.0, 2.0, 2.5, 4, 8, 24, 48, 96, and 168 h after the first infusion and within 0.5 h before the second and fifth infusions. Ametumumab concentration was detected in serum samples using a ligand binding assay based on antigen–antibody binding interactions. The concentration of Ametumumab was determined to use human EGFR antigen or anti-cetuximab antibody as a capture or detection reagent. The trough concentration and steady-state determination of numerous cycles were used to perform multiple-dose PK investigations.

Immunogenicity

MSD (Meso Scale Discovery)-based bridging electro-chemiluminescence immunoassay was used to detect the anti-drug antibodies (ADAs) (Bridging-ECLIA). Ametumumab and biotin–Ametumumab were utilized as capture and detection reagents, respectively, to assess the presence of ADAs in serum samples.

Efficacy

The size of the lesions was determined to use as imaging in accordance with RECIST 1.1 recommendations. At all follow-up stages, the imaging methods and parameters remained consistent. The effectiveness was assessed after the sixth administration of the multiple-dose phase and every 8 weeks thereafter.

Statistical analysis

All analyses were conducted using SAS 9.4.

According to the intention-to-treat analysis, the full analysis set (FAS) includes all patients who met the inclusion criteria and successfully utilized the medicine at least once. FAS was primarily used to examine baseline data, demographic information, and effectiveness.

Ametumumab’s PK set (PKS) is defined as individuals who have used it at least once and have PK data after administration. Based on the PKS, PK analysis was performed. The concentration data were imported into the Phoenix WinNonlin 8.1 program, which was used to generate the non-compartment model’s major PK parameters.

Safety set (SS) refers to all patients who received at least one dose of Ametumumab and have completed the gathering of safety data after administration. Based on the SS, a safety analysis was undertaken. The approach of descriptive analysis was mostly applied.

Results

Subjects for research

Between 24 April 2017 and 9 July 2019, 22 participants were sequentially recruited from a single location in China using the dosage escalation concept. The demographics about the participants are shown in Table 1. In the aggregate, the mean age was 52.2 ± 13.6 years (21–69 years). Colorectal cancer patients account for 45.5% (10/22) of the eight kinds of solid tumors included. A prior regimen containing chemotherapy was administered to all patients, and 40.9% of patients received a prior regimen containing molecular-targeted treatment. All patients had their PK analyses for the single-dose phase completed. In all, 19 patients entered the phase of multiple dose, whereas eight entered the period of continuous administration (Table 1).

Table 1.

Subject demographics.

Characteristics	Dose level, mg/m2
	75 (N = 1)	150 (N = 6)	300 (N = 3)	450 (N = 3)	600 (N = 4)	750 (N = 5)	Total (N = 22)
Age, years, mean ± Std	52.0	60.0 ± 6.4	63.7 ± 8.4	52.0 ± 11.5	42.3 ± 20.5	44.2 ± 11.3	52.2 ± 13.6
Gender, No. (%)
Male	0	4 (66.7)	2 (66.7)	2 (66.7)	2 (50.0)	3 (60.0)	13 (59.1)
Female	1 (100.0)	2 (33.3)	1 (33.3)	1 (33.3)	2 (50.0)	2 (40.0)	9 (40.9)
ECOG at baseline, No. (%)
Grade 1	1 (100.0)	6 (100.0)	3 (100.0)	3 (100.0)	4 (100.0)	5 (100.0)	22 (100.0)
Tumor type, No. (%)
Lung cancer	0	1 (16.7)	0	1 (33.3)	1 (25.0)	1 (20.0)	4 (18.2)
Laryngeal cancer	0	1 (16.7)	0	0	1 (25.0)	0	2 (9.1)
Colorectal cancer	0	2 (33.3)	3 (100.0)	1(33.3)	1 (25.0)	3 (60.0)	10 (45.5)
Ovarian cancer	0	1 (16.7)	0	0	0	0	1 (4.6)
Gastric cancer	1 (100.0)	0	0	0	0	0	1 (4.6)
Pancreatic adenocarcinoma	0	1 (16.7)	0	1 (33.3)	0	0	2 (9.1)
Liver cancer	0	0	0	0	0	1 (20.0)	1 (4.6)
Adrenal neuroblastoma	0	0	0	0	1 (25.0)	0	1 (4.6)
Prior chemotherapy use, No. (%)	1 (100.0)	6 (100.0)	3 (100.0)	3 (100.0)	4 (100.0)	5 (100.0)	22 (100.0)
Prior molecular targeted therapy using, No. (%)	1 (100.0)	1 (16.7)	0	2 (66.7)	2 (50.0)	3 (60.0)	9 (40.9)

ECOG, Eastern Cooperative Oncology Group.

DLT and MTD

DLT was not observed in any patients at any single dosage of 75–750 mg/m². The MTD was not attained at the highest dosage (750 mg/m²) in this study.

Safety

Each of the 22 patients had adverse effects. Seven patients had grade 3 AEs (31.8%). Only one occurrence of grade 3 hypertension may be associated with Ametumumab, and it occurred during the continuous dosing phase and did not meet the DLT criteria. The remained six patients with grade 3 AEs were not or may not have been connected to Ametumumab (Table 2). In all, 15 patients (68.18%) had AEs associated with Ametumumab (Table 3). The most frequently reported AEs associated with Ametumumab (⩾10%) were headache (36.36%), proteinuria (27.27%), rash (13.64%), dizziness (13.64%), fever (13.64%), leukopenia (13.64%), and vomiting (13.64%). Other AEs associated with Ametumumab (<10%) were nausea (9.09%), acne-like dermatitis (9.09%), and neutropenia (9.09%). Except for one episode of hypertension (grade 3), all other Ametumumab-related AEs were mild or moderate, and were classified as grade 1 or 2 in severity. There were no notifications of serious infusion response (SIR) patients throughout the trial period. Four patients (18.2%) had serious AEs (SAEs) unrelated to Ametumumab (including potential irrelevance) but associated with disease progression (Table 2). One patient in the 750 mg/m² dosage group died of an unrelated reason (Table 2). This patient with colon cancer participated in the 750 mg/m² dose group, who had completed the single-dose phase, no DLT or other AEs within 28 days of the DLT observation period after the first dosage, but in the multiple dose trials, the patient withdraws his consent from this study, and the investigator considered the patient’s disease progression. And 1 month later, we knew that an AE of Grade 5 death occurred through telephone follow-up visit, the investigator assessed that the death of this case was related to the progress of the disease, but not related to Ametumumab. A summary of AEs is displayed in Table 3.

Table 2.

Grade 3 and above AEs.

AEs	Dose level, mg/m2	N (%)	CTCAE			Related to Ametumumab				DLT
			Grade 3	Grade 4	Grade 5	Related	Perhaps related	Perhaps irrelevant	Irrelevant
Intestinal obstruction	150	1 (4.55%)	1					1		No
Anemia	600	1 (4.55%)	1					1		No
Pyemia	600	1 (4.55%)	1					1		No
ALT increaseda	150	1 (4.55%)	1						1	No
AST increaseda	150	1 (4.55%)	1						1	No
Blood bilirubin increased	150	1 (4.55%)	1						1	No
Death	750	1 (4.55%)			1				1	No
Hypertension	300	1 (4.55%)	1				1			No
Total		7 (31.82%)	6		1		1	3	4

AEs, adverse events; ALT, alanine transaminase; AST, aspartate aminotransferase; CTCAE, Common Terminology Criteria for Adverse Events; DLT, dose-limiting toxicity.

^aALT increased and AST increased in the same subject.

Table 3.

Ametumumab-related AEs.

MedDRA-preferred term, N (%)	75 mg/m2 (N = 1)		150 mg/m2 (N = 6)		300 mg/m2 (N = 3)		450 mg/m2 (N = 3)		600 mg/m2 (N = 4)		750 mg/m2 (N = 5)		Overall (N = 22)
	All grades	Grade ⩾ 3	All grades	Grade ⩾ 3	All grades	Grade ⩾ 3	All grades	Grade ⩾ 3	All grades	Grade ⩾ 3	All grades	Grade ⩾ 3	All grades	Grade ⩾ 3
Headache	0	0	1 (16.7)	0	0	0	1 (33.3)	0	3 (75)	0	4 (80)	4 (80)	8 (36.36)	0
Proteinuria	1 (100)	0	0	0	0	0	1 (33.3)	0	2 (50)	0	1 (20)	0	6 (27.27)	0
Rash	0	0	1 (16.7)	0	0	0	1 (33.3)	0	0	0	1 (20)	0	3 (13.64)	0
Fever	0	0	0	0	0	0	0	0	2 (50)	0	1 (20)	0	3 (13.64)	0
Dizziness	0	0	0	0	0	0	0	0	2 (50)	1(20)	0	0	3 (13.64)	0
Vomiting	0	0	0	0	0	0	0	0	1 (25)	0	2 (40)	0	3 (13.64)	0
Leukopenia	1 (100)	0	1 (16.7)	0	0	0	0	0	1 (25)	0	0	0	3 (13.64)	0
Acne-like rash	0	0	0	0	0	0	0	0	0	0	2 (40)	0	2 (9.09)	0
Nausea	0	0	0	0	0	0	0	0	0	0	2 (40)	0	2 (9.09)	0
Hypertension	0	0	1 (16.7)	0	0	1 (33.3)	0	0	0	0	0	0	1 (4.55)	1 (4.55)
Neutropenia	0		1 (16.7)	0	0	0	0	0	1 (25)	0	0	0	2 (9.09)	0
Paronychia	0	0	0	0	0	0	1 (33.3)	0	0	0	0	0	1 (4.55)	0
Ejection fraction decreased	0	0	0	0	0	0	0	0	1 (25)	0	0	0	1 (4.55)	0
Blood bilirubin increased	0	0	1 (16.7)	0	0	0	0	0	0	0	0	0	1 (4.55)	0

AEs, adverse events; MedDRA, Medical Dictionary for Regulatory Activities.

Pharmacokinetics

Following a single dosage of Ametumumab in the range of 75–750 mg/m2, the Ametumumab concentration peaked between 2.34 ± 0.26 h and 6.59 ± 8.56 h and subsequently decreased (Table 4). At 672 h, the majority of participants’ Ametumumab concentrations were close to baseline values. The mean terminal half-life (T_1/2) varied from 82.91 ± 24.34 h to 198.16 ± 24.29 h. We can find the rising drug exposure levels when increasing doses of 75–600 mg/m2 were used. Figure 1(b) to (d) provides a straightforward linear association between important PK parameters [area under the curve (AUC)_last, AUC_{0 − ∞}, and C_max] and dosage levels.

Table 4.

Ametumumab PK exposure parameters during the single-dose phase.

PK parameter	Ametumumab dose (mg/m2)*
	75 mg/m2	150 mg/m2	300 mg/m2	450 mg/m2	600 mg/m2	750 mg/m2
Cmax (μg/mL)	35.01	96.57 ± 38.20	209.33 ± 10.79	252.00 ± 37.51	328.00 ± 51.61	557.60 ± 121.38
AUC0 − ∞ (h*μg/mL)	4623.59	10128.34 ± 3692.09	29326.01 ± 6977.12	39286.74 ± 405.01	56201.74 ± 14460.06	100898.98 ± 14486.30
Tmax (h)	2.5	6.59 ± 8.56	2.34 ± 0.26	2.49 ± 0.03	2.51 ± 0.01	3.50 ± 2.53
T1/2 (h)	125.62	82.91 ± 24.34	122.30 ± 41.63	124.24 ± 16.41	146.39 ± 29.83	198.16 ± 24.29
CL/F (mL/h/m2)	16.22	17.09 ± 8.21	10.58 ± 2.24	11.46 ± 0.12	11.19 ± 2.69	7.57 ± 1.17
MRT0 − ∞ (h)	170.73	130.04 ± 31.67	176.93 ± 62.09	190.03 ± 0.31	209.38 ± 32.94	273.19 ± 39.74

^*Ametumumab PK exposure parameters during the single-dose phase.

AUC, area under the curve; PK, pharmacokinetics.

Figure. 1.

Ametumumab PK of single-dose phase. (a) Mean concentration–time profiles for each dose group of Ametumumab for single-dose phase (logarithmic graph) (N = 22). (b, c, and d) are the mean values of C_max, AUC_last, and AUC_{0 − ∞} at dose levels of 75–600 mg/m² (N = 19).

AUC, area under the curve; PK, pharmacokinetics.

With regards to the multiple-dose phase, after the sixth administration, the mean concentration (C_{ss, av}) and AUC of concentration–time from 0 to 168 h (AUC_{ss,0–168 h}) in the steady state increased dose proportionally from 75 to 750 mg/m². The C_{ss, av} and AUC_{ss,0–168 h} for 450 mg/m² were 297.26 µg/mL and 499399.23 h* µg/mL, respectively. T_1/2 in the steady state (T_{1/2, ss}) for doses 75-750 mg/m² ranged from 95.59 to 313 h (Table 5). For 450 mg/m², multiple-dose T_{1/2, ss} (125.30 ± 39.10) was similar to single-dose T_1/2 (124.24 ± 16.41). It was tentatively calculated that the fourth injection of 75–600 mg/m² attained a steady state. Figure 2 depicts the temporal curve of the average concentration in the multiple-dose period. There was drug accumulation following several administrations of all dosages, with the accumulation index (calculated based on AUC) between 1.8 and 2.5.

Table 5.

Ametumumab PK exposure parameters during the multiple-dose phase.

PK parameter	Ametumumab dose (mg/m2)*
	75 mg/m2	150 mg/m2	300 mg/m2	450 mg/m2	600 mg/m2	750 mg/m2
Cmax (μg/mL)	60.30	126.00 ± 6.00	317.33 ± 69.66	550.67 ± 209.87	705.67 ± 135.98	1034.00 ± 371.87
AUCss,0–168 h (h*µg/mL)	6513.69	13519.36 ± 3625.32	31109.50 ± 11682.52	49939.23 ± 17223.08	79528.67 ± 25442.74	110521.01 ± 30478.52
T1/2 (h)	313	95.59 ± 20.64	147.31 ± 76.70	125.30 ± 39.10	248.22 ± 75.47	161.70 ± 12.43
MRTss (h)	432.63	147.44 ± 33.24	226.44 ± 119.78	185.31 ± 49.26	348.98 ± 111.83	236.90 ± 26.93
Css,av (μg/mL)	38.77	80.47 ± 21.58	185.18 ± 69.54	297.26 ± 102.52	473.38 ± 151.44	657.86 ± 181.42

^*Ametumumab PK exposure parameters during the multiple-dose phase.

AUC_{0 − ∞}, area under the concentration–time curve from zero up to ∞ with extrapolation of the terminal phase; AUC_{ss,0–168 h}, area under the concentration–time curve from 0 to 168 h; CL/F, clearance divided by bioavailability; C_max, maximum concentration; C_ss,av, average plasma concentration of steady station; MRT_SS, mean residence time; T_max, time to reach maximum plasma concentration; T_1/2, terminal half-life.

Figure. 2.

Mean concentration–time profiles for each dose group of Ametumumab for multiple-dose phase (logarithmic graph) (N = 19).

Immunogenicity

ADA positivity was identified, we found just one reactive ADA-positive patient in the 750 mg/m² dosage group on the 22nd day following a single treatment. The other dosage groups were negative for ADA.

Efficacy

In all, 22 patients were evaluable for imaging assessment of tumor response and gene detection (Table 6). In total, 10 (45.5%) patients across all dosage groups had stable disease (SD), whereas 10 (45.5%) experienced disease progression (PD). There was a 45.5% success rate in illness control (disease control rate). The KRAS, NRAS, and BRAF genes were found to be absent in 85.7% of cases with SD.

Table 6.

Tumor progression and gene detection results.^a

Dose (mg/m2)	Type of tumor	Imaging evaluation of tumor	Gene detection			WT gene, N (%)b
			KRAS	NRAS	BRAF	KRAS	NRAS	BRAF
75	Gastric cancer	SD	WT	WT	WT	1 (100%)	1 (100%)	1 (100%)
150	Rectal cancer	PD*	WT	WT	WT	4 (66.7%)	6 (100%)	6 (100%)
	Hypopharyngeal carcinoma	PD	WT	WT	WT
	Rectal cancer	PD*	MUT	WT	WT
	Lung cancer	SD	WT	WT	WT
	Pancreatic cancer	PD*	MUT	WT	WT
	Ovarian cancer	SD	WT	WT	WT
300	Colon cancer	SD	WT	WT	WT	2 (66.7%)	3 (100%)	2 (66.7%)
	Colon cancer	SD	WT	WT	MUT
	Colon cancer	PD	MUT	WT	WT
450	Colon cancer	SD	WT	WT	WT	2 (66.7%)	3 (100%)	3 (100%)
	Pancreatic cancer	PD	MUT	WT	WT
	Lung squamous carcinoma	SD	WT	WT	WT
600	Laryngeal carcinoma	PD	WT	WT	WT	1 (50%)	2 (100%)	2 (100%)
	Colon cancer	PD	MUT	WT	WT
	Adrenal ganglioneuroblastoma	SD	NA	NA	NA
	Lung squamous carcinoma	SD	NA	NA	NA
750	Colon cancer	NA	WT	WT	WT	4 (100%)	4 (100%)	3 (75%)
	Rectal cancer	SD	NA	NA	NA
	Sigmoid colon cancer	NA	WT	WT	MUT
	Lung squamous carcinoma	PD	WT	WT	WT
	Hepatoid adenocarcinoma	PD	WT	WT	WT

^*Tumor progression and gene detection results.

^aAll imaging evaluations were performed after the sixth administration (approximately 10 weeks after the administration of single-dose phase) of multiple-dose phase except for three subjects of 150 mg/m² for whom the imaging evaluation was performed 4 weeks after the administration of single-dose phase due to early departure.

^bThe number and percentage of WT cases of KRAS, NRAS, and BRAF genes in each dose group were analyzed based on the total number of cases in which genetic test results were obtained.

MUT, mutant type; PD, disease progression; SD, stable disease; WT, wild type.

Discussion

This was the first time that Ametumumab was used in humans. DLT or MTD was not seen with the dosage increase from 75 to 750 mg/m². Furthermore, there were no SAEs associated with Ametumumab. Ametumumab’s immunogenicity was shown to be low in the ADA test. The PK characteristics were dose dependent and had a lengthy half-life. A preliminary effectiveness in the treatment of advanced solid tumors was shown by the weekly injection schedule. These findings are consistent with previous preclinical research, with promising results for advanced solid tumors, notably in colorectal carcinoma patients, in this phase Ia trial.

The primary objective of the initial human study is often to determine the MTD, although this is unachievable with many medications owing to their great safety, and DLT was also not seen or recognized at high doses or repeated clinical doses. In this study, no DLT was observed in the dose range from 75 to 750 mg/m²; therefore, the highest administered dose of 750 mg/m² did not reach the MTD. Major PK parameters (AUC_{0 − ∞} and C_max) and dose levels showed a dose-dependent simple linear relationship, and the 300–750 mg/m² dose level showed a curative effect meanwhile, especially according to the tumor progression imaging assessment results, two patients of each reached SD across 300, 450, 600 mg/m² dosage groups, and the patients from 300, 450, 600 mg/m² dosage groups gained more survival benefit than other groups (the efficacy data for both PFS and OS is shown in Supplemental Table S1). According to a theory¹⁸ and existing PK and pharmacodynamics (PD) data, the reasonable therapeutic dosage may be between 300 and 600 mg/m², although this has to be confirmed in future studies.

During this study, no clinically significant infusion responses, severe skin toxicity, gastrointestinal, respiratory, or nervous system AEs were noted in association with Ametumumab. The research did not include premedication with H1-antihistamine or corticosteroids, as cetuximab (Erbitux) often does. The black box warnings included in the Erbitux instructions include severe and lethal infusion responses and adverse effects such as cardiorespiratory arrest (incidence 2–3%) or sudden death. Clinical investigations have demonstrated a greater than 10% prevalence of mild to moderate infusion responses to Erbitux,^13,14,19,20 and the incidence of SIRs (grades 3 and 4) is as high as 3%.²⁰ Around 90% of SIRs develop during the first infusion, even when prophylactic antihistamines are given; Prophylactic antihistamines and corticosteroids are often administered prior to Erbitux administration to avoid and minimize SIRs.¹⁵ Clinical trials with Erbitux have shown that the most often reported adverse responses (⩾10%) include the neurological system, respiratory system, gastrointestinal system, metabolism and nutrition, skin and subcutaneous tissue, and other systems.^{13,14,19–28} The most often reported adverse effects (⩾25%, severity 1–4) include skin responses, headaches (19–38%), diarrhea (19–72%), and infection (13–44%). Over 80% of individuals treated with Erbitux are likely to have skin responses, and the incidence of severe (grade 3 or 4) acne-like rash is as high as 18%.¹⁵ The most frequently reported AEs to Ametumumab (⩾25%) were headache (36.36%) and proteinuria (27.27%), both of which were grade 1–2. Headache occurred more often in individuals receiving high doses (600 and 750 mg/m²), usually within 24 h of the first infusion and was associated with fever. Most of these symptoms resolved with oral acetaminophen or even without therapy. The responses did not recur after administration, and a lower immunogenicity and fewer adverse effects make it unnecessary to take any prophylactic medication. Given the mild or moderate proteinuria, no precautions were performed, and there were no complications after recovery.

A meta-analysis found that previously authorized anti-EGFR monoclonal antibodies raised the risk of hypomagnesemia, hypokalemia, and hypocalcemia considerably.²⁹ The incidence of hypomagnesemia, hypokalemia, and hypocalcemia in grades 1–4 induced by Erbitux was as high as 55%, 11%, and 11%, respectively; the frequencies of grades 3 and 4 were 17%, 7%, and 4%, respectively.¹⁵ Hypomagnesemia and associated electrolyte problems may arise days to months following the start of Erbitux therapy. Serum electrolytes, particularly magnesium, potassium, and calcium, should be monitored throughout and after Erbitux therapy; electrolytes should be replenished as needed. There were no cases of hypomagnesemia, hypokalemia, or hypocalcemia linked with Ametumumab during this phase Ia research.

Ametumumab is manufactured using a Chinese hamster ovary cell line that lacks the aberrant Fab glycosylation sites seen in cetuximab generated using the SP2/0 cell line. On the Fab fragment of cetuximab, a galactosealpha-1,3-galactose sugar inside a carbohydrate structure was observed to correspond with severe allergic events such as SIRs.^30–32 Most patients already had preexisting IgE antibodies specific for galactose-alpha-1,3-galactose sugars, an uncontrolled extrinsic factor that contributed to the negative effects. In summary, Ametumumab outperforms cetuximab in terms of immunogenicity and is safer due to the reduction in immunogenicity-related side events.

Panitumumab is a fully IgG2 anti-EGFR antibody, which is absent of the antibody-dependent cell-mediated cytotoxicity (ADCC) and complement dependent cytotoxicity (CDC) antitumor effect existed in IgG1 antibodies such as Ametumumab and cetuximab; meanwhile, the most common AEs include hypomagnesaemia, eye, skin, and gastrointestinal problems, which are related to the primary mode of action through the blockade of the EGFR. As reported, panitumumab exacerbated the incidence of grade 3/4 diarrhea. A meta-analysis by Petrelli et al. concluded that cetuximab and panitumumab have a similar burden of overall toxicity in terms of severe AEs, the individual safety profiles are distinct.³³ Panitumumab was associated with a higher rates of grade 3/4 skin toxicities, hypomagnesemia, fatal AEs, and treatment discontinuations, while cetuximab was associated with a higher rates of skin rash, infusion reactions, and gastrointestinal toxicity.³³

Herein, T_1/2 of the 300, 450, and 600 mg/m² dose groups during the multiple-dose phase were 147.31 ± 76.70 h, 125.3 ± 39.1 h, and 248.22 ± 75.47 h, respectively (Table 5). However, the steady-state half-life of cetuximab at the therapeutic dose is approximately 112 h (63–230 h).¹⁵ In addition, the findings of the preclinical investigation indicated that Ametumumab’s half-life is considerably extended after intravenous injection of the same dosage (7.5 mg/kg) of Ametumumab and cetuximab in the cynomolgus monkey.

In this study, patients with advanced solid malignancies in a total of eight different tumor types, such as colorectal cancer, gastric cancer, lung cancer, pancreatic cancer, ovarian cancer, laryngeal carcinoma, adrenal neuroblastoma, and hepatoid adenocarcinoma, were recruited. The estimated efficacy of SD was evident in each dosage group beginning with the first dose (75 mg/m²). Tumor shrinkage was detected in three patients, and each of these three patients received treatment for more than ten months, resulting in a benefit from longer survival. Ten instances of colorectal cancer were included in this investigation, seven of which had gene detection and tumor assessment data. Three instances of KRAS gene mutant cancers were classified as PD, three cases of KRAS gene wild-type tumors were classified as SD, and one case of KRAS gene wild-type tumor was classified as PD (Table 6) in the tumor radiologic response. The imaging assessment findings indicated that patients with colorectal cancer with wild-type RAS may be a preferable indication; however, patients with mutant RAS genes may benefit little, which is consistent with earlier research.^21,22 Due to the study’s primary limitation of a limited sample size, larger-scale investigations are necessary to demonstrate Ametumumab’s effectiveness.

Conclusion

In conclusion, our trial demonstrated that Ametumumab was well tolerated and safe in patients with advanced solid tumors who did not need prophylactic hormones or antihistamines. According to the study’s findings, the suggested dosage ranges from 300 to 600 mg/m² once a week or once every 2 weeks. Nonetheless, Ametumumab’s safety and effectiveness in colorectal cancer with RAS wild type need further investigation.