Facing increasingly high expectations as the front-runner in the PD-1/VEGF bispecific race, Summit Therapeutics and Akeso's ivonescimab looks to have risen to the occasion. The experimental treatment notched a key clinical win in a Phase III Chinese study that investors and physicians alike hope will bolster the chances of success for a separate late-stage global trial in patients with non–small-cell lung cancer (NSCLC).During Sunday's plenary session at the American Society of Clinical Oncology (ASCO) meeting, investigators on the HARMONi-6 study presented hotly anticipated overall survival (OS) results, which met statistical significance (see – Spotlight On: Lung cancer bispecifics poised to take centre stage at ASCO this year and Spotlight On: Five things to watch at ASCO).HARMONi-6 enrolled 532 patients with advanced squamous NSCLC to receive either ivonescimab or BeOne Medicines' PD-1 inhibitor Tevimbra (tislelizumab), both in combination with chemotherapy. At a media briefing ahead of the presentation, ASCO's lung cancer expert, David Spigel, called squamous NSCLC a disease with "largely unmet medical need," adding that "this group still often has a very poor prognosis, even with advanced therapies like chemotherapy and immunotherapy." Spigel is the chief scientific officer of the Sarah Cannon Research Institute in Tennessee.OS benefit of 4.2 monthsAs of the Feb. 27 data cut-off, patients taking ivonescimab achieved a median OS of 27.9 months versus 23.7 months for Tevimbra, translating to a 34% reduction in the risk of death (HR 0.66; p=0.0017) after a median follow-up of 21.4 months.Ahead of the ASCO readout, FirstWord spoke with Lyudmila Bazhenova, a medical oncologist and professor of medicine at University of California San Diego Moores Cancer Center, who said a six-month improvement in OS would be a "great" outcome for ivonescimab, though she added that she "would even be happy if we see an absolute benefit of four months" (see – KOL Views Q&A: Ivonescimab's HARMONi-3 update further tempers hopes for all-or-nothing prospects of PD-1/VEGF bispecifics).On the safety front, study investigators called ivonescimab's profile "comparable" to Tevimbra. About 69% of patients receiving the bispecific experienced a grade 3 or higher treatment-related adverse event (AE), with 5.3% discontinuing treatment, compared with rates of 58.9% and 4.5%, respectively, for the Tevimbra arm. The trial also looked at possibly VEGF-related any-grade AEs, which occurred more frequently in the experimental cohort than the comparator. Such AEs included proteinuria (42.5% vs 12.8%), haemorrhage (24.8% vs 12.1%), hypertension (14.7% vs 5.7%), arterial thromboembolism (1.5% vs 0%) and venous thromboembolism (0.8% vs 1.1%).Up next, a global stageThe findings provide important evidence that positive progression-free survival (PFS) data for PD-(L)1/VEGF inhibitors can translate to a meaningful OS benefit. At last year's European Society for Medical Oncology (ESMO) meeting, Summit and Akeso presented data showing that ivonescimab led to a median PFS of 11.1 months versus 6.9 months for Tevimbra — cutting the risk of disease progression or death by 40%.ASCO's positive OS readout could also be a much-needed confidence booster for Summit's global NSCLC study, HARMONi-3, after an update at the end of April seemed to shake investors. As part of its first-quarter earnings report, the drugmaker disclosed that a preplanned interim PFS analysis of the squamous cohort missed the bar for success, with a final PFS analysis to be conducted as planned in the second half of 2026.However, Spigel was cautious as to the applicability of the HARMONi-6 results — which he called "quite noteworthy" — to global patient populations. "It's hard to know how this [data] applies to a population of patients beyond [China]," he said. "Are there differences in ethnicity that affect how drugs like this work? We wait on other studies like the HARMONi-3 study, but these results are certainly very encouraging."While Summit — and physicians — wait for the HARMONi-3 data to inform a potential FDA approval for ivonescimab, competition within the PD-(L)1/VEGF class is heating up.BioNTech and Bristol Myers Squibb shared Phase II findings for their entrant, pumitamig, at ASCO, as did Pfizer for its own PD-1/VEGF bispecific, PF-08634404.In the ROSETTA Lung-02 trial, which enrolled both squamous and non-squamous NSCLC patients, pumitamig plus chemotherapy demonstrated a confirmed ORR of 52.5% in 40 evaluable patients. Pfizer's candidate, evaluated as a monotherapy in previously untreated patients with PD-L1–positive advanced NSCLC, showed a confirmed ORR of 67.6% in 34 evaluable patients (see – ASCO26: After ivonescimab stumble, rivals unveil their own bispecific data).And outside of the bispecific space, antibody-drug conjugates (ADC) are increasingly encroaching on their lung cancer territory. Merck & Co. and Kelun-Biotech posted Phase III data at ASCO for their ADC, sacituzumab tirumotecan (sac-TMT), which, given in combination with Keytruda (pembrolizumab), reduced the risk of disease progression or death by 65% versus the PD-1 inhibitor alone in patients with previously untreated PD-L1–positive metastatic NSCLC (see – Spotlight On: Merck & Co. and Kelun threaten to rain on ivonescimab's ASCO parade).