Why this name is on the tape
Tempus AI, Inc. (NASDAQ: TEM) is a Chicago diagnostics and pharma-data company. Moderna, Inc. (NASDAQ: MRNA) is a Cambridge mRNA shop. They are not co-developing a vaccine together. The tape mixed them on 19 August 2026 because Personalis, Inc. (NASDAQ: PSNL) — the lab Tempus has agreed to buy — has sequenced tumors for Merck and Moderna’s individualized neoantigen program since that program began.
A Phase 3 win for that program is evidence about a sequencing platform and an investigational therapy. It is not a Tempus product launch, not a Moderna supply contract on Tempus letterhead, and not an FDA approval. This article is the chain of contracts. A separate MarketNeon note covers Tempus’s Q2 lab print, the AstraZeneca model, and the Personalis price tag as a P&L story.
What Personalis actually does for the shot
Intismeran autogene — also called V940 or mRNA-4157 — is an investigational individualized neoantigen therapy jointly developed by Merck (NYSE: MRK) and Moderna. Each dose is built from a patient’s own tumor mutations. The lab’s job is to profile tumor and normal tissue, pick which mutated proteins (neoantigens) the immune system can see, and hand that list to Moderna’s mRNA platform. Personalis’s ImmunoID NeXT platform is the named tool Merck and Moderna have used from the start of clinical development. Each therapy encodes up to 34 neoantigens. Personalis is the profiling step. Moderna manufactures the RNA. Merck’s KEYTRUDA (pembrolizumab) is the checkpoint-inhibitor backbone in the combination trials.
That is a three-company stack: sequencer, mRNA factory, PD-1 antibody. Tempus sits on the stack only if and when the Personalis acquisition closes. Until then Personalis is still a separate public company, and Tempus’s live commercial link is the November 2023 partnership that already lets Tempus sell NeXT Personal as an MRD blood test — monitoring leftover cancer DNA, not writing the vaccine recipe.
The Personalis–Moderna–Merck book, before Tempus made an offer
On 19 December 2024 Personalis announced two related but separate deals. Merck agreed to buy $50 million of Personalis common stock in a private placement at $3.56 a share — about 14 million shares, on the order of 16.5% ownership at the time. Separately, Personalis signed a multi-year extension with Moderna to keep using ImmunoID NeXT on V940/mRNA-4157. Personalis’s CEO said the aim was to stay on the program through routine treatment of patients, not only trials. An equity stake and a platform extension are not the same as a manufacturing contract, and they are not Tempus’s contracts.
What Tempus signed in July 2026
On 20 July 2026 Tempus announced a definitive agreement to acquire the Personalis shares it does not already own at $16.25 per share, about $1.5 billion of enterprise value net of Tempus’s existing stake. The deal is structured as 100% stock, with Tempus able to pay up to half in cash. The exchange ratio floats, capped at 0.3356 Tempus shares per Personalis share. Close is expected late 2026 or early 2027, subject to Personalis shareholder approval, regulators, and other customary conditions. Personalis can walk if Tempus Class A trades below $46 before close. Preliminary Personalis Q2 revenue was $22.4 million, with 10,384 clinical tests in the quarter.
That acquisition is why TEM printed when the melanoma readout landed a month later. Tempus would be buying the MRD test it already commercializes and the tumor-profiling engine sitting under Merck and Moderna’s INT program. It would not be buying KEYTRUDA, Moderna’s manufacturing line, or an approved cancer vaccine. Guidance Tempus already gave for 2026 still excludes Personalis.
What INTerpath-001 actually showed
On 19 August 2026 Merck and Moderna reported topline Phase 3 results from INTerpath-001 (NCT05933577). The trial enrolled 1,137 patients with completely resected stage IIB–IV cutaneous melanoma and no prior systemic therapy, randomized 2:1 to intismeran plus KEYTRUDA versus KEYTRUDA alone. Intismeran was 1 mg every three weeks for up to nine doses; KEYTRUDA was 400 mg every six weeks for about a year. At a pre-specified interim analysis the combination met the primary endpoint of recurrence-free survival and a key secondary endpoint of distant metastasis-free survival, with statistically significant and clinically meaningful improvements versus KEYTRUDA alone. The companies called it the first positive Phase 3 readout for an individualized neoantigen therapy and for an mRNA-based cancer therapy. Safety was described as consistent with earlier combination studies, with no new signals. Overall survival is still being followed. Data are to be presented at a medical meeting and discussed with regulators — not filed as an approved label in that press release.
The Phase 3 print sits on top of KEYNOTE-942 / mRNA-4157-P201 Phase 2b, including five-year follow-up at ASCO 2026: a 49% reduction in the risk of recurrence or death (HR 0.51) and a 59% reduction in the risk of distant metastasis or death (HR 0.411) versus KEYTRUDA alone. Merck and Moderna are also running a broader INTerpath program — nine Phase 2 and Phase 3 trials across melanoma, non-small cell lung cancer, bladder cancer, and renal cell carcinoma. Those other tumors have not had this Phase 3 melanoma readout.
Names that print when this headline runs
These tickers usually move together when the sentence is “mRNA cancer vaccine.” They are not a ranked list. Each one sits on a different clock.
- TEM (Tempus AI) — agreed to buy Personalis. Already sells NeXT Personal MRD under a 2023 commercial partnership. Does not manufacture intismeran.
- PSNL (Personalis) — ImmunoID NeXT tumor profiling for V940/mRNA-4157 since the program started; NeXT Personal MRD. Still independent until the Tempus deal closes.
- MRNA (Moderna) — mRNA manufacturing partner on intismeran autogene, jointly with Merck.
- MRK (Merck) — KEYTRUDA backbone, co-developer, and a 2024 equity investor in Personalis.
What this does not tell you
A Phase 3 RFS and DMFS win is evidence that this combination beat KEYTRUDA alone in adjuvant high-risk melanoma on those endpoints at an interim look. It is not FDA approval, not overall-survival data, and not a result in lung, bladder, or kidney cancer. Merck and Moderna still have to present the full data and talk to regulators. Personalis’s role as the profiling lab does not automatically survive every commercial-scale manufacturing choice after a label, if a label comes.
Tempus’s $1.5 billion agreement is signed and not closed. Shareholder votes, regulators, a $46 Tempus-share floor, and integration all still sit ahead. Owning Personalis would put Tempus next to Merck and Moderna’s sequencing step. It would not make TEM a vaccine company and it would not put intismeran revenue into Tempus’s 2026 guide.
On MarketNeon, TEM is a ticker like any other: price, volume, crowd mentions, and headlines can run hot while the sequencer, the mRNA dose, and the acquisition sit on different clocks. This article is context for those prints. It does not rank the names, and it does not tell anyone to buy or sell.