Platinum resistant ovarian cancer treatment is changing as researchers study newer antibody-drug conjugates for patients whose cancer has progressed after platinum-based chemotherapy. One investigational medicine, Rina-S or rinatabart sesutecan, reported a 45.9% response rate in the RAINFOL-01 Phase 1/2 trial, but it is still not an approved standard treatment and must be confirmed in Phase 3 research.
Platinum-resistant ovarian cancer remains one of the most difficult stages of ovarian cancer treatment. Many patients have already received surgery, platinum chemotherapy, taxane-based chemotherapy, bevacizumab, PARP inhibitors, or targeted therapy before the cancer returns or progresses. At this point, families often begin searching for newer drugs, clinical trials, antibody-drug conjugates, and supportive care options that may help when standard choices become limited.
A new investigational antibody-drug conjugate called rinatabart sesutecan, also known as Rina-S, has now reported encouraging results in platinum-resistant ovarian cancer. The results were presented on 3 October 2026 at the International Gynecologic Cancer Society Congress in Montréal, Canada. In Part C of the RAINFOL-01 Phase 1/2 trial, Rina-S showed a 45.9% confirmed objective response rate in 109 heavily pretreated patients with platinum-resistant high-grade serous ovarian, primary peritoneal, or fallopian-tube cancer [1].
This is clinically important because platinum-resistant ovarian cancer usually has fewer effective treatment options than platinum-sensitive disease. A response rate close to 46% is an important signal in a heavily pretreated group, especially because the trial included patients who had already received multiple previous lines of therapy. However, the most important patient-facing message must remain clear: Rina-S is still investigational. It is not yet an approved standard treatment for platinum-resistant ovarian cancer, and these results still need confirmation in randomized Phase 3 evidence [1,2].
What Is Rina-S?
Rina-S is an FRα-targeted antibody-drug conjugate. FRα stands for folate receptor alpha, a protein found on the surface of many ovarian cancer cells. An antibody-drug conjugate is designed like a targeted delivery system. The antibody part helps guide the drug toward cancer cells expressing the target, while the attached payload delivers a cancer-killing medicine into or near the tumour cell.
In the case of Rina-S, the payload is related to topoisomerase-I inhibition, a mechanism that interferes with DNA processes required for cancer-cell growth and survival [1]. This is different from traditional chemotherapy, where the drug circulates more broadly through the body. The goal of antibody-drug conjugate treatment is to improve the therapeutic index by directing more of the active drug effect toward the tumour.
This does not mean that Rina-S is free from toxicity. It remains a powerful anticancer drug and can still affect normal tissues, blood counts, digestion, energy, and overall treatment tolerance. Therefore, its safety profile is as important as its tumour response data.
What Did the RAINFOL-01 Trial Show?
In Part C of the RAINFOL-01 Phase 1/2 trial, 109 patients received Rina-S at 120 mg/m² every three weeks as monotherapy. These patients had platinum-resistant high-grade serous ovarian cancer, primary peritoneal cancer, or fallopian-tube cancer. More than half had already received three or four previous treatment lines, making this a difficult-to-treat population [1].
The confirmed objective response rate was 45.9%, meaning that almost 46 out of every 100 treated patients had measurable tumour shrinkage according to trial assessment criteria. The study also reported five complete responses, which means that measurable cancer was no longer seen on trial imaging or assessment at that time. The median duration of response was 12.1 months, and the median progression-free survival was 9.5 months [1].
The duration of response is especially relevant for patients. In advanced cancer treatment, a tumour response that lasts only a few weeks may not translate into meaningful benefit. In this study, 51% of responders were still in response at one year, suggesting that some patients may have achieved durable disease control [1].
However, this result must be interpreted carefully. RAINFOL-01 Part C was an open-label Phase 1/2 cohort. Open-label means the doctors and patients knew which treatment was being given. It was not a completed randomized Phase 3 comparison against standard chemotherapy. Therefore, the data are promising, but they are not yet definitive.
Why the FRα Finding Is Important
One of the most interesting findings was that Rina-S showed antitumour activity across different levels of FRα expression, including patients with low FRα expression and even non-expressors. Activity was also reported in patients who had previously received mirvetuximab soravtansine, another FRα-targeted antibody-drug conjugate [1,3].
This matters because the currently approved FRα-directed drug, mirvetuximab soravtansine, is used for selected patients whose tumours are FRα-positive by an approved test. The FDA approved mirvetuximab for adult patients with FRα-positive, platinum-resistant epithelial ovarian, fallopian-tube, or primary peritoneal cancer after one to three prior systemic treatment regimens [4].
In the MIRASOL trial, mirvetuximab improved overall survival, progression-free survival, and objective response rate compared with investigator’s-choice chemotherapy in FRα-positive platinum-resistant ovarian cancer [4]. Therefore, FRα has already become a clinically important target in ovarian cancer.
The new question is whether Rina-S can provide benefit across a broader group of patients, including those with lower FRα expression or those previously exposed to FRα-directed therapy. This is scientifically interesting, but patients should not misunderstand it as proof that FRα testing is no longer needed. Biomarker testing, eligibility criteria, and treatment selection still depend on oncology guidance and trial protocol requirements.
How Rina-S Compares With Existing Treatment Thinking
For platinum-resistant ovarian cancer, treatment decisions are usually individualized. Factors include prior treatments, BRCA status, homologous recombination deficiency status, FRα expression, performance status, residual toxicity from earlier treatment, bowel involvement, ascites, liver and kidney function, and patient goals.
Standard chemotherapy options may include weekly paclitaxel, pegylated liposomal doxorubicin, topotecan, or gemcitabine. Bevacizumab may be used in selected settings depending on prior exposure, risk profile, and local approval. PARP inhibitors may be relevant earlier in the disease course, especially for patients with BRCA mutation or homologous recombination deficiency, but many patients in the platinum-resistant setting have already received them.
Rina-S is being studied because patients who have already moved through these treatment lines need better options. The RAINFOL-01 data are encouraging because all patients had already received bevacizumab and taxane therapy, nearly half had received a prior PARP inhibitor, and one-third had received prior mirvetuximab soravtansine [1].
This makes the result more clinically meaningful than a trial conducted only in treatment-naïve or lightly pretreated patients. Still, until Phase 3 results are available, it should be described as a promising investigational therapy, not as a proven replacement for current standard treatment.
Safety Findings Patients Should Understand
The safety data must be explained clearly because response rate alone is not enough for advanced cancer decision-making. In RAINFOL-01, common treatment-emergent adverse events included nausea, fatigue, vomiting, constipation, reduced appetite, abdominal pain, anaemia, neutropenia, low platelet count, and thrombocytopenia [1].
Serious adverse events occurred in approximately one-third of participants. Treatment discontinuation because of treatment-emergent adverse events occurred in 5.5% of patients. The report also stated that no safety signals for ocular toxicity, peripheral neuropathy, interstitial lung disease, or stomatitis were observed in this cohort [1].
This last point is relevant because some antibody-drug conjugates may have specific toxicity patterns. For example, mirvetuximab carries important warnings, including ocular toxicity, pneumonitis, and peripheral neuropathy [4]. The absence of a particular signal in an early or moderate-sized cohort is encouraging, but it does not prove that the risk can never appear. Larger studies and longer follow-up are still necessary.
For patients, the practical message is simple: Rina-S may be promising, but it must be used only through properly supervised clinical-trial or approved-access pathways. Blood counts, gastrointestinal symptoms, liver function, kidney function, infection risk, and overall strength need close monitoring.
What Is the RAINFOL-02 Phase 3 Trial?
The next major step is the RAINFOL-02 Phase 3 trial, which is designed to compare Rina-S against investigator’s-choice chemotherapy in platinum-resistant ovarian cancer [2,3]. This is the type of trial needed to answer the most important clinical questions.
A Phase 3 trial can show whether Rina-S is better than existing chemotherapy options, whether it improves progression-free survival, whether it improves overall survival, and whether the benefit is strong enough to justify the risks. It can also clarify which patients are most likely to benefit.
The RAINFOL-02 trial is especially important because patients may be enrolled regardless of FRα expression, according to trial reporting. This may help answer whether Rina-S can work beyond the population traditionally selected for FRα-positive treatment [3].
Until those results are available, doctors and patients should treat Rina-S as a clinical-trial option rather than a confirmed standard therapy.
What Patients Should Ask Their Oncologist
A patient with platinum-resistant ovarian cancer should not only ask whether a new drug has shown tumour response. The more important question is whether the patient personally fits the eligibility criteria and whether the expected benefit is realistic in their case.
Important discussion points include whether the tumour is high-grade serous, fallopian-tube, or primary peritoneal cancer; how many prior treatment lines have been used; whether bevacizumab, PARP inhibitors, or mirvetuximab have already been given; whether FRα testing has been performed; whether there is bowel obstruction, uncontrolled ascites, severe neuropathy, low blood counts, liver dysfunction, or kidney dysfunction; and whether a clinical trial is accessible in the patient’s country.
Patients should also ask whether the goal of treatment is tumour shrinkage, symptom control, delaying progression, improving quality of life, or gaining time for another option. In platinum-resistant ovarian cancer, treatment goals must be honest and measurable.
Ayurvedic and Integrative Support During Advanced Ovarian Cancer
For patients with advanced ovarian cancer, supportive care is not a secondary issue. Appetite loss, nausea, constipation, fatigue, low blood counts, pain, disturbed sleep, anxiety, and weakness can directly affect treatment tolerance and quality of life. This is where carefully planned integrative care may help, provided it does not interfere with oncology treatment.
In Ayurveda, supportive care may focus on Agni, meaning digestive and metabolic strength; Bala, meaning functional strength; and Ojas, meaning resilience and vitality. These concepts can guide individualized dietary support, digestion support, sleep support, strength preservation, and recovery planning. However, this must be done with caution during active chemotherapy, antibody-drug conjugate treatment, targeted therapy, or clinical-trial treatment.
Concentrated herbal extracts, bhasma preparations, high-dose antioxidants, immune-stimulating supplements, and over-the-counter herbal products should not be started without reviewing the patient’s oncology medicines, liver function, kidney function, platelet count, neutrophil count, bleeding risk, and trial restrictions. Herb-drug interactions may change drug metabolism, increase toxicity, worsen liver strain, or interfere with clinical-trial eligibility [5,6].
The safest position is balanced and patient-focused: tumour-directed decisions should remain under oncology supervision, while Ayurveda may be considered as supportive care for digestion, strength, sleep, appetite, recovery, and symptom burden when it is medically coordinated.
Clear Patient Takeaway
Rina-S is one of the most interesting investigational antibody-drug conjugates currently being studied in platinum-resistant ovarian cancer. The 45.9% confirmed response rate, five complete responses, 12.1-month median duration of response, and activity across FRα expression levels make the RAINFOL-01 data clinically important [1].
But this is not yet a cure claim and not yet standard treatment. The current evidence is from an open-label Phase 1/2 cohort. Patients should ask their oncologist about biomarker testing, standard treatment options, clinical trial availability, RAINFOL-02 eligibility, and supportive-care planning.
For families searching online, the key message is hope with accuracy: Rina-S may become an important future option for platinum-resistant ovarian cancer, but it still needs Phase 3 confirmation before it can be considered a proven treatment.
FAQs
Is Rina-S approved for platinum-resistant ovarian cancer?
No. Rina-S is still investigational. The 45.9% response rate was reported from the RAINFOL-01 Phase 1/2 programme, not from a completed Phase 3 approval trial. Patients should ask their oncologist whether a Rina-S clinical trial or another suitable trial is available.
Does a complete response mean ovarian cancer is cured?
A complete response means that measurable cancer is no longer visible by trial assessment at that time. It does not automatically mean permanent cure. Patients still need follow-up scans, CA-125 monitoring where appropriate, symptom review, and continued oncology supervision.
Why is response in low FRα expression important?
FRα-targeted treatment usually depends on whether the tumour expresses folate receptor alpha. Rina-S showing activity in low or absent FRα expression is scientifically important because it may broaden future treatment possibilities. However, this finding still requires Phase 3 confirmation.
Can a patient take Ayurveda during Rina-S or chemotherapy?
Ayurvedic supportive care may be considered only after reviewing the full oncology plan, blood counts, liver and kidney function, current medicines, and clinical-trial restrictions. It should support strength, digestion, sleep, and recovery, but it should not replace tumour-directed cancer treatment.
References
- Genmab A/S. (2026, October 3). Genmab announces rinatabart sesutecan (Rina-S) Phase 2 RAINFOL-01 results demonstrated durable and clinically meaningful responses in patients with platinum-resistant ovarian cancer. Brief: Official source for the 45.9% response rate, five complete responses, median duration of response, progression-free survival, FRα findings, and safety data. https://ir.genmab.com/news-releases/news-release-details/genmab-announces-rinatabart-sesutecan-rina-sr-phase-2-rainfoltm
- ClinicalTrials.gov. (2026). Study to assess the efficacy of Rina-S compared to treatment of investigator’s choice in participants with platinum-resistant ovarian cancer: RAINFOL-02, NCT06619236. Brief: Trial registry source for the ongoing Phase 3 confirmatory programme comparing Rina-S with investigator’s-choice chemotherapy. https://clinicaltrials.gov/study/NCT06619236
- Targeted Oncology. (2026, October 5). Rinatabart sesutecan shows durable responses in platinum-resistant ovarian cancer. Brief: Oncology news summary explaining RAINFOL-01 patient population, response results, prior therapy exposure, and RAINFOL-02 development. https://www.targetedonc.com/view/rinatabart-sesutecan-shows-durable-responses-in-platinum-resistant-ovarian-cancer
- U.S. Food and Drug Administration. (2024, March 22). FDA approves mirvetuximab soravtansine-gynx for FRα-positive, platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer. Brief: FDA approval source for the existing FRα-targeted ADC treatment context and MIRASOL outcomes. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-mirvetuximab-soravtansine-gynx-fra-positive-platinum-resistant-epithelial-ovarian
- Memorial Sloan Kettering Cancer Center. (2026). Herbs, botanicals & other products: Frequently asked questions. Brief: Patient-facing oncology resource explaining why herbs and supplements may interact with cancer treatment and should be reviewed with clinicians. https://www.mskcc.org/cancer-care/diagnosis-treatment/symptom-management/integrative-medicine/herbs/herbs-botanicals-other-products-faqs
- Gandhi, A., et al. (2025). Unraveling herb–drug interactions in cancer therapy. Brief: Modern review discussing herb-drug interaction risks in cancer care, including drug metabolism, toxicity, and treatment-safety concerns. https://pmc.ncbi.nlm.nih.gov/articles/PMC12609569/
