PLUS THERAPEUTICS, Inc.

Good afternoon, ladies and gentlemen. Welcome to the Plus Therapeutics first quarter 2023 results conference call. Before we begin, we want to advise you that over the course of the call and question and answer session, forward-looking statements will be made regarding events, trends, business prospects, and financial performance, which may affect Plus Therapeutics' future operating results and financial position. All such statements are subject to risks and uncertainties, including the risks and uncertainties described under the risk factors section included in Plus Therapeutics annual report on Form 10-K and quarterly reports on Form 10-Q filed with the Securities and Exchange Commission from time to time. Plus Therapeutics advises you to review these risk factors in considering such statements. plus Therapeutics assumes no responsibility to update or revise any forward-looking statements to reflect events, trends, or circumstances after the date they are made. It is now my pleasure to turn the floor over to Dr. Mark Hedrick, plus Therapeutics President and Chief Executive Officer. Sir, you may begin.

Thank you, Jonathan. Good afternoon, everyone, and thank you once again for taking the time to join us today. as we provide an overview of recent business highlights and discuss our 2023 first quarter financial results. Joining me for the call today is Dr. Norman LaFrance, our Chief Medical Officer, and Andrew Sims, our Chief Financial Officer. I'll begin the call by reviewing our recent clinical and regulatory progress with a focus on the first quarter, and then turn the call over to Andrew to review our financials. Dr. LaFrance then will be joining us for Q&A. I can say we had a very productive start to 2023, highlighted by the increased enrollment momentum of our two lead programs in glioblastoma, or GBM, and leptomeningeal metastases, or LM. Starting with our GBM program and the Phase IIb trial, we are actively enrolling the Phase IIb clinical trial of rhenium obispumata in patients with small to medium-sized GBM tumors with a 20-centimeter, a 20cc, or a 20-milliliter cutoff. The single administered dose is 22.3 millicuries and 8.8 mLs, and the primary endpoint is overall survival, and there are a number of typical secondary endpoints, such as safety, objective response rate, partial response, and PFS at six months. Our goal is to complete Phase 2b enrollment of 31 patients by the end of 2024, and we are on schedule to do that. The trial is substantially funded by the National Cancer Institute at present for up to 55 patients at five sites. We are in the process of negotiating with the NIH to expand the trial sites to a number sufficient such that we can rapidly complete the Phase 2b and a presumed Phase III pivotal trial thereafter. In parallel to our discussions with the NIH, we are actively engaged with over 17 sites in the U.S. and Europe as possible new trial sites, and we're pleased with the interest we see in that trial. Now, regarding the ongoing Phase I GBM dose escalation trial for larger and more complex tumors over 20 cc. As announced, we have now enrolled the three required dose escalation patients in cohort 8 and administered a dose of 41.5 millicuries and 16.3 milliliters. That dose and volume are approximately double the dose and volume used in the current phase 2b. In total, since trial initiation, 27 patients have been enrolled in just the phase one dose escalation portion of the trial. Since we have yet to reach a phase one trial stopping point based on reaching a maximum tolerated dose, we have several options in terms of how we may proceed. We are in the process of analyzing the data from cohort seven and eight from the phase one and intend to provide guidance on next steps once the data is analyzed and a plan is formulated. Now, a bit of a side note or perspective on this phase one dose escalation portion of the trial. Irrespective of whatever we do in terms of next steps, I want to highlight the fact that we are breaking new ground in medicine here with this trial. Specifically, if you look in terms of the amount of radiation and volume that we are now safely delivering to a single cerebral hemisphere in a patient that may have a tumor of 30 cc's or more. It's truly remarkable that we've been able to do that safely, including administering up to 740 gray in a single administration administered dose to the tumor. Don't want that to be lost here. And we haven't reached a maximum tolerated dose. So moving on to the LM development program. As announced, we completed part A of the phase one respect LM trial. In total thus far, have been treated across three dosing cohorts. And in fact, one patient was retreated under compassionate use protocol. The maximum administered dose thus far, and that was administered in cohort three, is 26.4 millicuries up from 6.6 millicuries that were delivered in the three patients in cohort one. At the cohort three dose, the computed maximum absorbed dose to the CSF is approximately 200 gray of radiation. Thus far, no dose-limiting toxicities have been observed, and the safety profile, as is in our GBM trial, appears to be favorable, and nine of the 10 LM patients treated thus far remain alive. The go-forward plan is to conduct a cohort three DSMB meeting followed by an FDA type C meeting to finalize the dosing regime for part B of the phase one as requested by the FDA during our original negotiations for the trial. Presumably, we will continue to dose escalate through a single administration until a maximum tolerated dose is reached and then incorporate multiple doses over time thereafter. it's helpful to us to be able to have already treated one patient under compassionate use with two separate treatments. Separately, we're working on a single institution leptomeningeal metastases trial specifically for melanoma primaries and more about that as that develops. In addition, we plan to treat patients at the cohort three dose to gain additional safety and efficacy data until cohort four is approved And we will consider, as I mentioned, selectively retreating patients after the stipulated trial follow-up period of 90 days if patient and their physician feel it would be . As with the GBM trials, we are focused heavily in 2023 on onboarding new LM trial sites for the Phase I Part B, and 20 sites are currently under evaluation. Finally, PLUS continues to receive support for the program through our $17.6 million SEPRINT grant awarded last year. Now, regarding our development program for pediatric brain cancer, based on the back-and-forth communication we've had thus far with the FDA, which goes back almost a year, we expect to submit an updated investigational new drug application soon for what will be called the RESPECT, PBC Phase 1 Safety Dose Finding and Efficacy Study of Rhenium Obispumata for Two Pediatric Brain Tumors, specifically ependymoma and high-grade glioma. The FDA has essentially signed off on the clinical trial plan, but they've asked for additional safety data from the human trial, which we've put together and will be refiling as part of that IAD update. That will be submitted in conjunction with the lead academic institution that we've been working with along the way on this trial, and that's Lurie Children's Hospital of Northwestern University in Chicago. Now, a bit about supply chain. It's very important that we have drug available for any patient we treat and that we're at a stage appropriate to where we are in the development clinically as it relates to our supply chain. So, maintaining a robust and redundant supply chain for rhenium-obistumate supply is critical. In previous quarters, we have added key suppliers and consummated important CMO relationships as we have developed GMP drug for our trials. We anticipate continuing in 2023 to expand those relationships and, in fact, add new relationships such that we are ready for a potential phase three trial or alternatively an accelerated approval tract if that presents itself. Now a bit about commercial planning. Commercial go-to-market planning, including relevant medical economic research, billing and coding considerations, and ultimately drug pricing and commercial launch planning decisions, are proceeding in the background consistent with our stage of development. Now, regarding our novel in-license radioembolic microparticle technology, RNL-BAM. Recall that in 2022, we closed the license for RNL-BAM, transferred the technology, successfully manufactured the product, and completed product feasibility work in a human ex vivo kidney perfusion model. We also sought the FDA's opinion on regulatory designation at the end of 2022. Currently, we have an active dialogue ongoing with the FDA, including a previously submitted preliminary request for designation. The outcome of that determination will dictate many of the next steps in preclinical development program and the timeline to the clinic, specifically whether that ultimate designation is a device, drug, or combination product. Notably, the legacy products that have been out for 20 plus years our devices, we think likely this should be regulated as a drug, but we await the outcome of that back and forth. So with that summary on our clinical development programs, I'll turn the floor over to our Chief Financial Officer, Andrew Sims, who will review the financials. Andrew?

Thank you, Mark. Good afternoon, everyone. Please refer to our press release issued earlier today for a summary of our financial results for the 2023 first quarter ended March 31, 2023. As of March 31, 2023, cash and cash equivalents were $12.7 million compared to $18.1 million as of December 31, 2022. In addition to current cash on hand, the company benefits from grant awards of $3 million from the NIH and $17.6 million from CPREC. The company also has discretionary or stockholder-approved access to capital from its ATM and equity line of credit of at least $49 million. In aggregate, these capital sources could provide sufficient capital to fund currently planned and anticipated activities through 2025, if fully utilized. The company recognized $506,000 of grant revenue in the first quarter of 2023, which represents a separate share of costs incurred to fund a portion of our LM clinical program. Total operating expenses for the first quarter of 2023 were 5.2 million compared to total operating expenses of 3.9 million for the same period the prior year. The increase is due primarily to a 750,000 license payment to Nano TX Corp for successfully meeting a key clinical milestone and related clinical expenses due to increased enrollment in the company's lead development programs. Interest expense decreased from $198,000 for the first quarter of 2022 to $134,000 for the first quarter of 2023. This decrease reflects the continued principal pay down that commenced in November 2021 on the company's Oxford debt. Net loss for the quarter for the first quarter of 2023 was 4.8 million, or 14 cents per share, compared to a net loss of 4.1 million, or 19 cents per share, for the same period the prior year. Now I'll turn it back to Mark.