Peritoneal carcinomatosis (PC) representing dissemination of malignant cells throughout the peritoneum is one of the most severe manifestations of metastasis in colorectal cancer (CRC) and gastric cancer (GC). This disorder is associated with the extremely poor prognosis, a sharp decline in the quality of life, and the limited effectiveness of standard systemic approaches. As for CRC, PC is detected in 10–15% of patients when first diagnosed with stage IV cancer, аnd up to 20–25% of patients develop peritoneal dissemination later in life; the median overall survival (OS) without treatment does not exceed 5–7 months, increasing to only 10–16 months with the use of the advanced FOLFOX or FOLFIRI regimen [1, 2].

Cytoreductive surgery with the hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) is the only method proven to prolong the lives of selected patients (Peritoneal Cancer Index [PCI] < 20), ensuring the 5-year OS of 30–40%, but the share of candidates for this intervention does not exceed 20–30%. As for GC, the situation is even more dramatic: synchronous PC is reported in 25–35% of patients, metachronous multiple gastric cancer post gastrectomy is developed by 30–50% of patients, and the median OS without treatment is as short as 3–4 months, reaching 6–12 months with the platinumbased chemotherapy [3]. Immunotherapy with PD-1 inhibitors demonstrates dubious results due to the immunosuppressive peritoneal microenvironment, which dictates an urgent need for the drugs capable of crossing pharmacokinetic barriers.

In this context, there is an expectedly growing interest in the minimally invasive pressurized intraperitoneal aerosol chemotherapy (PIPAC) technique. The method involves the laparoscopic spraying of cytostatics as an aerosol under stable pneumoperitoneum (12 mmHg), ensuring the homogeneous distribution of the drug and overcoming interstitial hypertension in tumor nodules with minimal systemic absorption [4]. The PIPAC clinical efficacy has been convincingly proven by prospective studies: an objective histological regression based on the Peritoneal Regression Grading Score (PRGS) scores is achieved in 60–75% of cases, ascites control is reported in 70–85% of patients, and the median OS of individuals with the GC-associated metachronous carcinomatosis reaches 15.4 months [5]. The procedure allows one to repeat interventions every 4–6 weeks, conduct dynamic molecular-genetic profiling of the tumor via biopsy; it can be safely combined with the systemic therapy to allow one to implement the total cytoreduction concept [6].

However, modern PIPAC therapy has severe limitations. The penetration depth of standard drugs in within 1–3 mm, which makes it impossible for chemotherapy drugs to interact with large foci of carcinomatosis and leads to selection of chemoresistant clones [7]. With multiple cycles, cumulative toxicity is manifested by the cisplatin-induced nephrotoxicity, doxorubicin-induced cardiotoxicity, and oxaliplatin-induced peripheral neuropathy, which limits the number of possible procedures [8]. These factors determine the need to develop innovative agents extending beyond the scope of traditional cytostatics. The range of modern pharmacological agents includes peptide biomolecules capable of penetrating the hypovascularized stroma [9]. Among these, conjugates BT1718 (targeting MT1-MMP/MMP14) and PEN-221 (targeting the SSTR2 receptor), the LTX-315oncolytic peptide, which induces immunogenic cell death, as well as the 177Lu-DOTATATE radionuclide preparations and peptides for the CLDN18.2 target for targeted radionuclide therapy are distinguished [10-12].

The domestic synthetic peptide preparation "Ing-Ras," developed at the Russian Scientific Center of Roentgenoradiology of the Ministry of Health of the Russian Federation is of special interest. Its mechanism of action is based on the highly specific allosteric binding of switch II of the mutant KRAS effector domain (including the G12D and G12V mutations), which consequently blocks the interaction of the cancer protein with RAF, interrupting the MAPK/Erk signaling cascades [13]. Incorporation of D-amino acids into the peptide structure ensures its proteolytic stability in the ascitic fluid aggressive environment, amphiphilicity makes it possible to cross the cell membrane without any transport systems, and selectivity for KRAS-dependent cells guarantees minimal toxicity for normal tissues [14].

Thus, integration of targeted peptide platforms, such as "Ing-Ras," into PIPAC protocols signifies the transition from the переход from palliative symptom management to a strategy for the long-term cancer management. The ability of these molecules to penetrate the deep layers of tumor implants can potentially transform the natural course of unresectable peritoneal carcinomatosis, significantly increasing the median overall survival of the cohort of patients with poor prognosis.

The study aimed to assess the efficacy of the “Ing-Ras” targeted peptide intraperitoneally administered by the PIPAC method to patients with the disseminated GI tumors based on the long-term follow-up for 30 months after the follow-up phase termination.

METHODS

An original drug, the “Ing-Ras” peptide Ras-GTPase inhibitor, was developed and clinically tested for the first time at the Russian Scientific Center of Roentgenoradiology. “Ing-Ras” has a targeted effect on the molecular target; it can effectively enter the cell due to incorporation of the internalizible sequence (СРР, cell penetrating peptides) in the structure [13]. Primary efficacy assessment was one of the task of the 2nd stage of the phase I/IIa of the protocol of the clinical trial (CT) No. 2022-1-“IngRas” “The Prospective Open-Label Nonrandomized Multicenter Phase I/IIa Trial with the Adaptive Design of Safety, Tolerability, and Primary Efficacy, with Determination of the Maximum Tolerated Dose of the Drug Based on the RAS-GTPase Inhibitor (“Ing-Ras”) for Treatment of Patients Diagnosed with Gastrointestinal Tumors, Including Patients with Peritoneal Carcinomatosis”.

The I/IIa phase of the CT was divided into two stage; the main tasks of the 1^st stage were as follows: to assess the “IngRas” druf tolerability and safety, to determine the maximum tolerated dose, and to analyze the drug pharmacokinetics when intraperitoneally administered by the pressurized intraperitoneal aerosol chemotherapy (PIPAC) method to patients diagnosed with with gastrointestinal tumors, including peritoneal carcinomatosis.

Main inclusion criteria: previous surgery due to stage Т3–Т4 gastric cancer (GC), stage Т3–Т4 colon or rectal cancer; progression of the previously radially treated GC or colorectal cancer in the form of isolated peritoneal carcinomatosis; submitted patient’s written informed concent; age 18–75 years; adequate laboratory indicators and the ECOG status not exceeding 2.

Exclusion criteria: systemic metastasis (including in the CNS); malignant tumors of other localizations; decompensated concomitant disorders (CCF NYHA class ≥ III, uncontrolled hypertension, hepatic or renal failure, liver cirrhosis, Child-Pugh class A-С); acute infections (including HIV and hepatitis В/С) or severe blood clotting disorders; pregnancy or lactation; recently conducted chemotherapy and radiotherapy (less thn 4 weeks ago); administration of therapeutic doses of anticoagulants; severe peripheral neuropathy; mental disorders or social factors hindering adherence to the protocol; estimated life expectancy of less than 3 months, taking part in another trial in the last months or the fact of having any other condition (at the discretion of the researcher).

The patient was excluded from the study in cases of the informed consent withdrawal, the emergence of dose-limiting toxicity (at the 1^st stage) or adverse events preventing from taking part in the trial, pregnancy, erroneous enrollment, protocol violation, or the need to prescribe prohibited therapy, as well as in cases when the continued participation ran counter to the patient’s interests, when the contact with the patient was lost or the entire trial was terminated by the Sponsor or regulatory authorities.

At stage I it was planned to enroll up to 18 patients with the sequential enrollment of patients at each dose level in accordance with the “3 + 3” scheme.

As a result, a total of 11 patients were enrolled at stage I:

A total of 4 patients were included in the 1st cohort (PI dose 0.45 mg/kg);

A total of 3 patients were included in the 2^nd cohort (PI dose 0.9 mg/kg);

A total of 4 patients were included in the 3^rd cohort (PI dose 1.8 mg/kg).

Additional patients were included in the 1^st and 3^rd cohorts due to premature withdrawal of patients from these cohorts; the premature withdrawal was not associated with the doselimiting toxicity manifestations.

At stage II the data of 35 patients meeting all the inclusion critetria and having no noninclusion criteria were included in the study and analyzed. Considering the small number of patients and the fact that at the 1^st stage patients of the 3^rd cohort received the same “Ing-Ras” regimen (administration of two doses of 1.8 mg/kg), the data of these patients were used for efficacy assessment in this paper. The distribution of patients with the established diagnosis of colorectal cancer (CRC) is provided in tab. 1.

Table tab. 2 provides the data for patients diagnosed with GC.

Historical control group (at stage II): patients diagnosed with the gastrointestinal tumor complicated by peritoneal carcinomatosis or high risk of this complication post surgery with subsequent chemotherapy.

Statistical processing

The analysis was performed in R version 4.2.2 (R Core Team, 2023) using RStudio 2023.06.1. All the statistical tests were applied to the population enrolled, in accordance with the previously established definitions of the groups to be analyzed. The Kaplan–Meier estimator was used for efficacy assessment. Primary efficacy parameters were as follows: one- and two-year overall survival, cumilative rate of recurrence, and recurrence time.

Then a comparative assessment of the efficacy of treatment with the “Ing-Ras” drug inctraperitoneally administered by the PIPAC method relative to the historical control data was performed.

The historical control database for this paper was created retrospectively based on the analysis of the data published in the publicly available medical literature and specialized international registries.

The database creation process consisted of two steps:

1. Determination of comparability criteria. To ensure the comparison validity, historical cohorts were selected that strictly matched the key prognostic parameters of the studied group.

The main selection criteria were as follows:

• diagnosis: CRC or GC;
• disease stage: stage III–IV, including isolated peritoneal carcinomatosis post cytoreduction interventions;
• preceding treatment: patients after surgery (primary tumor resection), who received standard systemic chemotherapy (FOLFOX/FOLFIRI regimens in CRC, platinum-based regimens in GC);
• ECOG status: patient’s functional status score not exceeding 2;
• time frame: the data were selected from the papers spanning the last 5–7 years to rule out the influence of outdated treatment protocols on survival outcomes.

2. International cancer registries were used as sources of population-based and cohort-based indicators: SEER (USA, statistics for 2026) [15–16], Cancer Research UK [17–19]; national Russian registries [20–21], data of the American Cancer Society (ACS, Cancer Facts & Figure reports 2025– 2026) [22–26]. Results of large meta-analyses and reviews, key randomized phase III trials [27–37], for example, prospective studies of KRAS G12C inhibitors, providing up-to-date median progression-free survival values.
3. Mean values and ranges for the following endpoints were retrieved from the selected papers:

• one- and two-year overall survival.
• disease progression rate.
• cumilative rate of recurrence (DFS) in the 1^st ans 2^nd years of follow-up.
• median relapse-free survival (PFS) from the date of diagnosis and the date of surgery.

RESULTS

Safety assessment conducted based on the phase I data [38] showed the following:

• the dose-limiting toxicity was not achieved with the dose of 1.8 mg/kg;
• significant changes: crude protein (p = 0.00028), leukocytes (p = 0.007), lymphocytes (p = 0.0008) are within normal ranges;
• stable ECG and ECHO indicators;
• adverse events: short-term body temperature increase, negligible pain;
• favorable safety profile compared to chemotherapy (standard regimens yield the grade 3–4 toxicity in 40–60% of cases).

The “Ing-Ras” drug primary efficacy analysis conducted 30 months after the end of the phase I/IIa CT follow-up period allowed us to more thoroughly assess the number of important parameters and extend the results of the “Ing-Ras” primary efficacy assessment performed 12 months after the CT [39].

Table tab. 3 presents the results of comparing the “Ing-Ras” group with the publicly available historical data.

For patients with the established diagnosis of CRC it was shown that this group was characterized by the large share of female patients (76%), not characteristic of a statistical distribution. According to official statistics, males 15–30% more often suffer from colorectal cancer, which is due to a combination of behavioral factors (higher prevalence of smoking and alcohol abuse), features of the hormonal status and iron metabolism, as well as differences in the diet [40]. A total of 47.62% of patients had distant metastasis; 23.81% had peritoneal carcinomatosis, which corresponds to the extremely poor prognosis in the comparison cohort. Despite the severity of the baseline population’s condition, the one-year overall survival reached 95.24%, which was significantly higher compared to historical values for the same stages varying within the range of 65–85% [41]. The two-year survival was 80.95%, while the literature data on the standard chemotherapy suggest the range of only 50–65%.

The reported disease progression rate is 28.57%, which is significantly lower compared to the 40–60% experted for the generalized CRC forms. The relapse-free survival values also suggest fundamental changes in the natural disease course: the average remission duration since the diagnosis was 44.16 months, and the duration since surgery was 40.71 months, while in the world’s practive the median survival of individuals with stage IV disease does not exceed 12–18 months. The recurrence rate in the 1^st year of follow-up was minimal: as low as 4.72% vs. typical 20–30% in the comparison cohort.

A comparative analysis with modern foreign targeted agents confirms the test drug high therapeutic potential. Selective KRAS G12C inhibitors, such as sotorasib, adagrasib, and divarasib, demonstrate an objective response within the range of 9.7–29.1% and the median progression-free survival (PFS) about 4–6.5 months, while being limited to a narrow molecular mutation subtype.

Males prevailed in the group of GC in the “Ing-Ras” phase I/IIa clinical trial (65%), which is consistent with the general epidemiological indicators for GC. The cohort was characterized by the highly aggressive neoplastic process, which was confirmed by the fact of distant merastasis in 23.53% of patients and peritoneal carcinomatosis (an extremely negative prognostic factor) in 47.06% of participants (the fiveyear survival of individuals with carcinomatosis is below 10%). Despite the disease severity in the source cohort, the inclusion of the “Ing-Ras” RAS-GTPase peptide inhibitor in the combination therapy regimen made it possible to achieve the one-year survival of 76.47%, which was considerably higher compared to the historical values for the stage IV stage (historically not exceeding 40–60%). The two-year overall survival reached 47.06%, while the literature data on standard chemotherapy regimens suggest the range of only 20–30%. The median two-year overall survival calculated by linear interpolation was 13.24 months.

The disease progression rate in the follow-up period was 52.94%, showing the decrease by 60–80% relative to the expected population-based indicators. The relapse-free survival values also reflect the significantly longer time of the disease management: the average remission duration since the diagnosis is 26.44 months and the duration since surgery is 25.99 months, which is higher compared to the historical control (median 9–12 months for disseminated GC). The reported recurrence rate is 23.53% in the 1^st year and 29.41% in the 2^nd year, which is lower compared to the typical indicators of 30–50% and 15–30%, respectively.

Long-term primary efficacy assessment depending on the tumor histological subtype

The analysis of the distribution of patients based on the histological disease type conducted within the framework of the “Ing-Ras” drug phase IIa clinical trial has revealed significant differences in the genesis and prognostic potential of the studied CRC and GC. Classic epithelial tumors prevailed in the total sample including 38 patients with the locally advanced and metastatic forms of gastrointestinal malignant neoplasms (tab. 4).

In the CRC group (n = 21), morphological structure was represented primarily by adenocarcinomas of various grades: well-differentiated forms (G1) were reported in six patients (28.57%), moderately differentiated (G2) — in nine patients (42.86%), while poorly differentiated adenocarcinoma (G3) was reported only once (4.76%). In five patients (23.81%), grade was not specified in their source documents. Note that despite the presence of extremely adverse factors, such as peritoneal carcinomatosis (23.81%) and distant metastasis (47.62%), in this subgroup, the large share of moderately and well differentiated tumors is correlated to the unprecedented survival rates: the one-year overall survival reaches 95.24%, and the two-year survival is 80.95%. The disease progression rate for the follow-up period turned out to be minimal: it was 28.57%, which was significantly lower compared to the historical data for the stage III–IV disease (40–60%).

The GC cohort (n = 17) histological profile demonstrates another pattern reflecting a more aggressive disease phenotype. In terms of morphology, the tumor was highly heterogeneous: along with classic adenocarcinomas (well-differentiated G1 — 2 cases; moderately differentiated G2 — 4 cases; poorly differentiated G3 — 3 cases), there was a considerable share of signet ring cell carcinoma — 7 cases (41.18% of the entire GC group), as well as one case of adenocarcinoma not otherwise specified.The high rate of the signet ring cell variant, historically associated with the infiltrative growth, early lymphogenic metastasis, and low sensitivity to standard chemotherapy regimens, suggests that the studied population was a group with unfavorable prognosis. However, The “Ing-Ras” therapeutic effect made it possible to achieve the one-year overall survival of 76.47% and the two-year survival of 47.06%, while the progression rate decreased to 52.94% vs. 60–80% expected based on the population registries.

The comparative analysis of the therapy efficacy depending on the histological subtype suggests that the “Ing-Ras” RASGTPase peptide inhibitor retains high activity regardless of the cell anaplasia degree, but the most pronounced clinical effect is reported in individuals with the classic intestinal-type adenocarcinoma. This is confirmed by the comparison of relapse-free survival rates: as for CRC, the average remission duration since the diagnosis was 44.16 months, while the value for GC was significantly lower — 26.44 months, which in terms of biology was determined by the baseline aggressive nature of poorly differentiated and signet ring cell forms. It is important to emphasize the fundamental difference of the “IngRas” action profile from that of selective foreign first-generation KRAS inhibitors (sotorasib, adagrasib, divarasib), the efficacy of these is limited by the narrow spectrum of the G12C found in only 3–4% of CRC patients. Since the “Ing-Ras” mechanism of action is focused on the direct inhibition of the RAS-GTPase itself, the drug can potentially be used in individuals with the broad allelic spectrum of mutations (KRAS/NRAS G12D, G12V, G13D) underlying the pathogenesis of most histological cancer types analyzed.

DISCUSSION

The data yielded by the phase I/IIa clinical trial demonstrate an unprecedented improvement in long-term survival outcomes in patients with disseminated colorectal cancer (CRC) and gastric cancer (GC) complicated by peritoneal carcinomatosis. The achieved two-year overall survival of 80.95% in CRC and 47.06% in GC is significantly higher compared to the historical control values (50–65 and 20–30%, respectively), which makes it possible to consider “Ing-Ras” as a potentially transforming approach to treatment of the cohort with poor prognosis.

High therapy efficacy is determined by several factors. First, intraperitoneal administration of the drug ensures high local concentration of the active substance in dissemination foci by crossing the ascitic fluid pharmacokinetic barrier of overcoming the interstitial hypertension in tumor nodules [4, 42]. Second, the RAS-GTPase peptide inhibitor mechanism of action is fundamentally different from that of selective low molecular weight first-generation KRAS inhibitors (sotorasib, adagrasib).

While foreign analogues target only the narrow G12C mutation subtype (found only in 3–4% of CRC patients) and demonstrate the median progression-free survival (PFS) of about 4–6.5 months, “Ing-Ras” implements the allosterick blockage of the switch II domain of the GTPase itself. This determines its potential activity against the broad spectrum of driver mutations KRAS/NRAS (G12D, G12V, G13D) underlying the pathogenesis of most histological GIT cancer types analyzed [13].

The histological profile analysis confirms biological validity of the results: despite the presence of highly aggressive phenotypes, such as signet-ring cell carcinoma (41.18% of the GC group) and poorly differentiated adenocarcinomas, the drug retains high cytostatic activity. It is noteworthy that the therapeutic effect is correlated to the grade: the most pronounced increase in the median relapse-free survival is reported for the classic intestinal adenocarcinoma type (up to 44.16 months in CRC), while the values for poorly differentiated forms are lower, which reflects the tumor baseline biological potential.

Study limitations

Despite the significance of the results obtained, the interpretation of those is limited by a number of factors. Comparison with the historical cohorts from international registries (SEER, NCI) and national databases does not rule out the systematic selection bias due to the retrospective nature of the control group and the heterogeneity of prior lines of therapy. Small study sample (n = 38) reduces the statistical power of subgroup analyses and limits the external validity of the findings for the general population of patients with carcinomatosis. Morphological heterogeneity of the cohort, including a significant share of phenotypes with unfavorable prognosis (signet-ring cell carcinoma), is one more factor, which makes it difficult to extrapolate the data on standard adenocarcinoma forms. The period of safety assessment was limited to the clinical trial active phase, which could be insufficient to reveal the delayed toxicity of the drugs targeting the fundamental cell proliferation signaling pathways.

The above limitations dictate the need to conduct extended phase III trials to finally confirm the “Ing-Ras” drug clinical efficacy and long-term safety.

CONCLUSIONS

Thus, findings of the multicenter prospective phase I/IIa study suggest high clinical efficacy and favorable safety profile of the “Ing-Ras” RAS-GTPase peptide inhibitor intraperitoneally administered by the PIPAC method to patients with disseminated forms of colorectal and gastric cancer. The inclusion of the drug in the combination therapy regimen made it possible to overcome resistance even in subgroups with poor prognosis, including patients with the signet-ring cell GC and peritoneal carcinomatosis, ensuring the statistically and clinically significant increase in the one- and two-year overall survival relative to the historical control. The fact that the “Ing-Ras” mechanism of action based on the allosteric blockage of the GTPase domain is fundamentally different from the highly specific low molecular weight first-generation KRAS inhibitors determines its potential activity against the broad spectrum of driver mutations (KRAS/ NRAS G12D, G12V, G13D), which is confirmed by the therapeutic effect preservation regardless of the tumor cell anaplasia degree. However, considering the comparison retrospective nature, small sample size, and the lack of the randomized control and molecular stratification, the findings should be considered as preliminary. The reported high objective response rate and the control over ascites syndrome substantiate the need to conduct extended prospective phase III trials with the strict stratification based on histological and genetic biomarkers in order to finally confirm the targeted approach efficacy.