A Phase I Study of K-001 in Patients with Advanced Pancreatic Ductal Adenocarcinoma

Background: K-001 is an oral antitumor drug made from active ingredients of marine microorganisms. The current study aimed to evaluate safety and antitumor activity of K-001 in patients with advanced pancreatic ductal adenocarcinoma (PDAC). Methods: In this phase I, open-label trial, patients with advanced PDAC were recruited to a dose-escalation study in a standard 3+3 design. K-001 was administered twice daily in 4-week cycles, and dose escalation from 1350mg to 2160mg twice daily was evaluated. Physical examination and laboratory tests were done at screening and then weekly. The safety, dose-limiting toxicity (DLT), and maximum tolerated dose (MTD) of K-001 were assessed, and tumor response was estimated by Response Evaluation Criteria in Solid Tumor (RECIST). Results: Eighteen patients with advanced PDAC were screened, and twelve eligible patients were analyzed in the study. No DLT was observed. Totally, 47 adverse events (AEs) presented, and 14 drug-related AEs were reported in 7 patients, including 8 grade 1 events (57.1%) and 6 grade 2 events (42.9%). There was no grade 3 or 4 drug-related AE. In these 14 drug-related AEs, the most frequent ones were dyspepsia (21.4%), followed by atulence, constipation, and haemorrhoids bleeding (above 10% of each). Among all 12 patients, 10 patients (83.3%) maintained stable disease (SD), and 2 patients (16.7%) had progressive disease (PD). The objective response rate (ORR) was 0% and the disease control rate (DCR) was 83.3%. Conclusions: K-001 has and tolerability, as well as meaningful antitumor activity in advanced PDAC patients. Further evaluation of K-001 in phase II/III appears warranted. The current study was a phase I, open-label, single-center, dose-escalation clinical trial to determine the dose limited toxicity (DLT), the maximum tolerated dose (MTD) and the recommended dose (RD) for phase II/III trials, as well as the preliminary antitumor effects of K-001 in patients with advanced PDAC. The study was registered


Background
Pancreatic ductal adenocarcinoma (PDAC), also called pancreatic cancer, is among the most lethal cancer types world-wide with high mortality that almost closely parallels incidence, and is chemoresistant with less than 10% response rate to standard treatment [1]. Most PDAC patients who accept surgeon will relapse within one or two years, and their 5-year survival rate is less than 5% (the data has not uctuated signi cantly in the past 20 years). It has been estimated that PDAC may emerge as the second leading cause of cancer-related deaths by 2030 [2]. Particularly, about 85% of PDAC patients have already developed into incurable metastatic or locally advanced stage at the time of diagnosis [3]. Thus, chemotharapy-based comprehensive treatment is essential for PDAC patients, but the options are quite limited.
Compared with the rapid development of therapies for other cancer types, the treatment of pancreatic cancer, especially pancreatic ductal adenocarcinoma (PDAC), has been lacking in clinical progress. Mutant targeting and immunological therapies have shown e cacy or promise for certain types of cancer, but have not yet achieved similar results for pancreatic cancer [4][5][6][7]. Gemcitabine (GEM) has replaced uorouracil as the standard rst-line treatment since 1997, with the primary endpoint of "clinical bene t responses" including measurements of pain, performance status, and weight [8]. The tolerance of GEM was quite well, but the e cacy was unsatisfactory with 5.65 months of median overall survival (OS) and 18% of the 1year OS rate. Thereafter, many combinations of GEM with a variety of cytotoxic and targeted agents have been investigated, but no added bene t was observed in OS [9][10][11][12][13][14]. In 2007, Erlotinib plus GEM got a positive result statistically, but the median OS was only 6.24 months in combination group as compared with 5.91 months in GEM group [15]. In 2011, a phase III study showed that irinotecan, oxaliplatin, and leucovorin-modulated uorouracil (FOLFIRINOX) signi cantly improved the median OS compared to GEM (11.1 months vs 6.8 months) [16]. But the toxicities, such as neutropenia, diarrhea, and peripheral neuropathy were also signi cantly increased in FOLFIRINOX group, limiting the widespread use of FOLFIRINOX in Asian or patients with poor performance status. In 2013, a phase III trial in Japan and Taiwan showed that S-1 was not inferiority to GEM in median OS [17]. Another blockbuster study showed that nab-paclitaxel plus GEM signi cantly improved the median OS and progression-free survival (PFS), with acceptable tolerance [18]. For second line therapy, nanoliposomal irinotecan in combination with uorouracil and folinic acid prolonged the median OS [19]. Clinical studies in recent years have exhibited some degree of progress on e cacy of PDAC, nonetheless, toxic effects and tolerance are still the major concern in the treatments, especially for patients of several line therapies, or patients with poor performance status, who are intolerable to mono or multiple chemotherapy.
It is obvious that a safe, effective, and low toxic drug is highly demanded in PDAC treatment. Existing studies have shown that antitumor drugs screened from natural products are more promising for the demand than that from synthetic ones, due to their less toxic side effects [20]. K-001 is a biological compound made from active ingredients of marine microorganisms. The main components of K-001 are peptidoglycan (PGN) and its molecular weight is more than 100,000 daltons. The preclinical studies showed that K-001 was non-toxic or slightly toxic substances. In the previous phase I study of K-001 on multiple kinds of advanced refractory solid tumors, four doses were tested (670mg, 1350mg, 2025mg and 2700mg daily), and dose limited toxicity (DLT) was not observed. Moreover, the study showed that K-001 could improve performance status, appetite and quality of life, which are also highly demanded for PDAC. Based on those prior studies, the current study focused on the safety and antitumor activity of oral drug K-001 in patients with advanced PDAC.

Methods
The current study was a phase I, open-label, single-center, dose-escalation clinical trial to determine the dose limited toxicity (DLT), the maximum tolerated dose (MTD) and the recommended dose (RD) for phase II/III trials, as well as the preliminary antitumor effects of K-001 in patients with advanced PDAC. The study was registered with the US National Library of Medicine (ClinicalTrials.gov) as NCT02720666.
Patients were excluded on criteria of (1) non-adenocarcinoma of pancreatic tumors; (2) the target lesion had been treated by radiotherapy with no progression prior to the current trial; (3) central nervous system or leptomeningeal metastases; (4) Vater's ampullary carcinoma or biliary adenocarcinoma; (5) partial or complete intestinal obstruction; (6) a history of any other malignancy within ve years, excepted: a) a consecutive 5-year disease free survival from single surgery of other malignancies or b) cured cutaneous basal cell carcinoma or cured in situ carcinoma of the cervix; (7) received major surgery within 4 weeks; 8) infected with HIV, hepatitis B or hepatitis C; (9) having serious concomitant diseases. Treatment Using the standard 3 + 3 design, this trial consisted of four escalating dose levels (1350mg, 1620mg, 1890mg and 2160mg BID) and corresponding four cohorts (A, B, C, and D) of three patients, with three additional candidates for each cohort as necessary. Each cohort was treated at only one dose level, and allowed to continue if patients were receiving clinical bene t. The cohort A was orally administered the starting dose of K-001 twice daily for 4 weeks as a circle, then the subsequent cohorts (B, C and D) were treated respectively at the increasing dose levels that had been xed in advance. Only after the observation of one dose level was completed, can the trial at next higher dose level be carried out. Two or more dose cohorts may not be administered simultaneously.
Based on previous study results, the starting dose was the maximum one of the previous study, therefore a conservative incremental percent was set up, which was lower than what the improved Fibonacci's method recommended (cohorts, dose levels and increment percents exhibited in Table 1). Adverse events (AEs) were graded using the National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0 (NCI CTCAE v4.0) [22], and the relationship of AEs to the study drug was evaluated. Dose limiting toxicity (DLT) was de ned as any grade 3 AE or above that was de nitely, or probably related to K-001 administration. The maximum tolerated dose (MTD) was de ned as the highest dose level at which ≤ 33% of patients experience DLT [23].
If no DLT was observed, the trial escalated to the next dose cohort. If one of the three patients experienced a DLT at a certain dose level, three more patients would be administered at the same level, and patients with DLT should immediately be discontinued with medication and withdrawn from the trial; if DLT no longer presented, the trial proceeded at the next upper dose level; if DLT was still observed, the trial was closed, and all patients were followed for safety at day 28 after closure of the trial.

Assessment
Medical histories, disease characteristics and demographic data were collected at screening. The primary endpoints of this trial were safety and tolerability of the study drug, which were measured by adverse events (AEs), vital sign, electrocardiogram, and laboratory tests at baseline and on days 8, 15 A total of eighteen advanced PDAC patients were screened for this study, and six of them did not meet the inclusion criteria.
Twelve eligible patients were analyzed in the study and two of them did not return on the day 56. The baseline characteristics are presented in Table 2. Median age of the twelve patients was 62 years (range, 53-67 years) and eight (67%) of them were male. Eight patients (67%) were on stage IV. Three patients (25.0%) did not receive any previous chemotherapy.   (Table 3), with dyspepsia (21.4%) as the most frequent one, followed by atulence, constipation, and haemorrhoids bleeding (above 10% of each).
Besides, the correlation between the number of AEs and the dose levels was not signi cant (p = 0.334, 2-tailed), indicating that AEs were not dose dependent (AEs and dose levels exhibited in Table 4). In this phase I study, no DLT of oral K-001 with grade 3 or above drug-related AE was observed in patients during the escalating treatment cycles. Therefore, the MTD of K-001can be initially de ned as 1350mg-twice-daily for subsequent phase II/III studies. Antitumor activity According to the RECIST 1.0 criteria, all the 12 patients were evaluable for best overall response on day 29, and 10 patients were evaluable on day 56. Among the 12 patients, no patient presented complete response (CR) or partial response (PR), 10 patients (83.3%) maintained stable disease (SD), and 2 patients (16.7%) had progressive disease (PD). The objective response rate (ORR) was 0% and the 4-week disease control rate (DCR) was 83.3% (95% con dence interval [CI], 56.0%-97.0%). The percent change in tumor size from baseline by dose cohort was shown in Table 5. Changes of NRS score, QoL, and C-reactive protein (CRP) at baseline and on day 29, day 56 (2 patients not evaluable-16.7%) was also shown in Table 5. Compared to their baselines, NRS scores obtained relieved or stable in 8 patients (66.7%) on day 29, and in 6 patients (50.0%) on day 56, among which 3 patients did not need to take analgesics. QoL scores kept stable or improved in 6 patients (50.0%) on day 29, and in 7 patients (58.3%) on day 56. CRP levels were decreased or stable in 3 patients (25.0%) and increased in 9 patients (75.0%) on day 29, and decreased or stable in 1 patient (8.3%) and increased in 9 patients (75.0%). Furthermore, the results of paired samples t test (Table 6) indicated that on the whole, NRS, QoL, and CRP were increased on day 29 and day 56, compared to their baselines respectively, but did not reach the signi cant level. That is, NRS, QoL, and CRP remained stable during these periods.

Discussion
At present, the recommended rst-line treatments are mainly GEM, nab-paclitaxel, Capecitabine, S-1, 5-Fu/LV, and FOLFIRINOX [5,[8][9][10][11][12][16][17][18]. But the proportion of those patients, who are sustainable to single drug chemotherapy, is low, and who are applicable to combined chemotherapy, is even lower. And for those with poor performance status, the treatment options are even few. Furthermore, quiet few PDAC patients could receive nanoliposomal irinotecan as second line treatment, and the third line treatments of PDAC are even de ciency [19]. Thus a safe, effective, and low toxic drug is urgently needed in PDAC.
Clinical studies in recent years have con rmed that the e cacy of FOLFIRINOX in advanced PDAC is signi cantly better than that of GEM. At the same time, however, the incidence of grade 3 or 4 neutropenia, febrile neutropenia, thrombocytopenia, diarrhea, and sensory neuropathy associated with the FOLFIRINOX was signi cantly higher than that associated with GEM. In addition, two patients even died of treatment-related factors [16]. The current study con rmed that K-001 is quite well tolerated in PDAC patients, and no dose limited toxicity (DLT) was observed in the treatment cycles. During the trial, the drug-related (de nitely or probably) AEs were grade 1-2, mainly manifested as gastrointestinal reactions, and the symptoms were relieved or disappeared after appropriate treatments. All the AEs did not interfere with the dose escalation in the trial. The outcomes of the current study demonstrated that K-001 is very safe for PDAC patients.
Although e cacy was not the primary endpoint of the current trial, objective response rate (ORR), disease control rate (DCR), and other indicators of clinical bene t (NRS, QoL, and CRP) were evaluated to provide clues for subsequent phase II/III studies. In the current trial, the DCR of K-001 reached 83.3% (95% CI, 56.0%-97.0%), with more than 80% of the enrolled patients exhibited either tumor shrinkage or stabilization according to the RECIST 1.0 criteria (Fig. 1) Consent for publication: All authors agreed to submit for consideration for publication in this journal.
Availability of data and materials: the public data and materials could be found on line (https://clinicaltrials.gov/ct2/show/NCT02720666.) Competing Interests: The authors declare that they have no competing interests.